JAVA语言程序设计基础课后习题第四章

//exercise 4.1
package fourthchapterexercise1;
import java.util.Scanner;
public class first {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int integer=0,sum=0,positive=0,negative=0;
        Scanner in=new Scanner(System.in);
        System.out.println("Enter an int value,the program exits if the input is 0:");
        while(true){
            integer=in.nextInt();
            if(integer==0)
                break;
            else if(integer>0)
                positive++;
            else
                negative++;
            sum=sum+integer;
        }
        double average=(double)sum/(positive+negative);
        System.out.println("The number of positives is "+positive);
        System.out.println("The number of negatives is "+negative);
        System.out.println("The total is "+sum);
        System.out.println("The average is "+average);
    }

}


//exercise 4.2
package fourthchapterexercise1;

import java.util.Scanner;

public class second {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        final int NUMBER_OF_QUESTIONS=10;
        
        int correctCount=0;
        int count=0;
        
        long startTime=System.currentTimeMillis();
        
        String output="";
        
        Scanner in=new Scanner(System.in);
        
        //The main program
        while (count<NUMBER_OF_QUESTIONS){
            //0-15 random number
            int number1=(int)(Math.random()*15+1);
            int number2=(int)(Math.random()*15+1);
                        
            //input expression
            System.out.print("What is "+number1+" + "+number2+"? ");
            
            //get answer
            int answer=in.nextInt();
            
            //judge answer
            if(number1+number2==answer){
                System.out.println("You are correct!");
                correctCount++;
            }
            else 
                System.out.println("Your answer is wrong.\n"+number1+" + "+number2+" sh"
                        + "ould be "+(number1+number2));
            
            //count
            count++;
            
            output +="\n"+number1+" + "+number2+"="+answer+((number1+number2==answer)?" cor"
                    + "rect":" wrong");
        }
        
        long endTime=System.currentTimeMillis();
        long testTime=endTime-startTime;
        
        System.out.println("Correct count is "+correctCount+"\nTest time is "+testTime/1000+" seco"
                + "nds\n"+output);
    }

}


//exercise 4.3
package fourthchapterexercise1;
public class third {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("千克\t\t英镑");
        for(int i=0;i<100;i++){
            System.out.println(2*i+1+"\t\t"+(2*i+1)*2.2);
        }
    }

}


//exercise 4.4
package fourthchapterexercise1;

public class fourth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("英里\t\t千米");
        for(int i=1;i<=10;i++){
            System.out.println(i+"\t\t"+i*1.609);
        }
    }

}


//exercise 4.5
package fourthchapterexercise1;

public class fifth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("千克\t\t镑\t\t磅\t\t千克");
        int pound=20;
        for(int i=0;i<100;i++){
            System.out.println(2*i+1+"\t\t"+(int)((2*i+1)*2.2*100)/100.0+"\t"
                    + "\t"+pound+"\t\t"+(int)(pound/2.2*100)/100.0);
            pound+=5;
        }
    }

}


//exercise 4.6
package fourthchapterexercise1;

public class sixth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("英里\t\t千米\t\t英里\t\t千米");
        int pound=20;
        for(int i=0;i<10;i++){
            System.out.println(i+"\t\t"+(int)(i*1.609*1000)/1000.0+"\t"
                    + "\t"+pound+"\t\t"+(int)(pound/1.609*1000)/1000.0);
            pound+=5;
        }
    }

}


//exercise 4.7
package fourthchapterexercise1;

public class seventh {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double tuition=10000;
        for(int i=0;i<10;i++){
            tuition *= (1+0.05);
            
        }
        System.out.println("after ten year,tuition is "+tuition);
        
        double sum=0;
        for(int i=0;i<4;i++){
            sum += tuition;
            tuition *= (1+0.05);
        }
        System.out.println("tuition of four year is "+sum);
    }

}


//exercise 4.8
package fourthchapterexercise1;
import java.util.Scanner;
public class eighth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input number of students is ");
        int number =in.nextInt();
        String maxname=null;
        int max=0;
        for(int i=0;i<number;i++){
            System.out.print("please input student‘s name and score:");
            String name =in.next();
            int score=in.nextInt();
            if(score>max)
                maxname=name;
        }
        System.out.print("The most high score students name is :"+maxname);
    }

}


//exercise 4.9
package fourthchapterexercise1;
import java.util.Scanner;
public class ninth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input number of students is: ");
        int number =in.nextInt();
        String maxname=null,secondname=null;
        int max=0;
        int secondhigh=0;
        for(int i=0;i<number;i++){
            System.out.print("please input student‘s name and score:");
            String name =in.next();
            int score=in.nextInt();
            if(score>max){
                maxname=name;
                max=score;
            }
            if(score>secondhigh&&score!=max){
                secondname=name;
                secondhigh=score;
            }
            
        }
        System.out.println("The most high score students name is :"+maxname);
        System.out.println("The second high score students name is :"+secondname);
    }

}

//exercise 4.10
package fourthchapterexercise1;
import java.util.Scanner;
public class tenth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int count=0;
        for (int i=100;i<=1000;i++){
            if(i%5==0&&i%6==0){
                System.out.print("\t"+i);
                count++;
                if(count%10==0)
                    System.out.println();
            }
        }
    }

}

//exercise 4.11
package fourthchapterexercise2;

public class first {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int count=0;
        for (int i=100;i<=200;i++){
            if(i%5==0^i%6==0){
                System.out.print("\t"+i);
                count++;
                if(count%10==0)
                    System.out.println();
            }
        }
    }

}

//exercise 4.12
package fourthchapterexercise2;

public class second {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int n=1;
        while(true){
            if(n*n>12000){
                System.out.println("The smallest integer is "+n);
                break;
            }
            n++;
        }
    }

}


//exercise 4.13
package fourthchapterexercise2;

public class third {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int n=1;
        while(true){
            if(n*n*n>12000){
                System.out.println("The smallest integer is "+(n-1));
                break;
            }
            n++;
        }
    }

}


//exercise 4.14
package fourthchapterexercise2;

public class fourth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int startascii=33;
        int count=0;
        while(startascii<=126){
            char output=(char)startascii;
            count++;
            System.out.print("\t"+output);
            if(count%10==0)
                System.out.println();
            startascii++;
        }
    }

}


//exercise 4.15
package fourthchapterexercise2;
import java.util.Scanner;
public class fifth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input two integer n1 and n2 :");
        int n1=in.nextInt();
        int n2=in.nextInt();
        int min;
        if(n1>n2)
            min=n2;
        else
            min=n1;
        while(true){
            if(n1%min==0&&n2%min==0){
                System.out.println("The greatest common divisor is "+min);
                break;
            }
            min--;
        }
    }

}


//exercise 4.16
package fourthchapterexercise2;
import java.util.Scanner;
public class sixth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input integer:");
        int integer=in.nextInt();
        System.out.print("The factor is :");
        while(true){
            for(int i=2;i<=integer;i++){
                if(integer%i==0){
                    System.out.print(i);
                    integer=integer/i;
                    if(integer==1)
                        System.out.print(".");
                    else
                        System.out.print(",");
                    break;
                }
            }
            if(integer==1)
                break;
        }
    }

}


//exercise 4.17
package fourthchapterexercise2;
import java.util.Scanner;
public class seventh {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        Scanner in=new Scanner(System.in);
        
        System.out.print("please input integer (0-15):");
        int input =in.nextInt();
        
        for(int i=1;i<=input;i++){
            
            for(int j=1;j<=input-i;j++){
                if(j==input-i){
                    System.out.print("\t");
                    break;
                }
                System.out.print("\t ");
            }
            
            for(int k=i;k>0;k--){
                
                if(k==1){
                    System.out.print(k);
                    break;
                }
                
                System.out.print(k+"\t");
            }
            
            for(int j=2;j<=i;j++){
                System.out.print("\t"+j);
            }
            
            System.out.println();
        }

    }

}


//exercise 4.18
package fourthchapterexercise2;

public class eighth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //pattern 1
        for(int i=1;i<=6;i++){
            for(int j=1;j<=i;j++){
                System.out.print(j+"\t");
            }
            System.out.println();
        }
        
        System.out.println();
        System.out.println();
        
        //pattern 2
        for(int i=1;i<=6;i++){
            for(int j=1;j<=7-i;j++){
                System.out.print(j+"\t");
            }
            System.out.println();
        }

        System.out.println();
        System.out.println();
        
        //pattern 3
        for(int i=1;i<=6;i++){
            for(int j=1;j<=6-i;j++){
                System.out.print(" \t");
            }
            for(int k=i;k>=1;k--){
                System.out.print(k+"\t");
            }
            System.out.println();
        }
        
        System.out.println();
        System.out.println();
        
        //pattern 4
        for(int i=1;i<=6;i++){
            for(int k=2;k<=i;k++){
                System.out.print(" \t");
            }
            for(int j=1;j<=7-i;j++){
                System.out.print(j+"\t");
            }
            System.out.println();
        }
    }

}

//exercise 4.19
package fourthchapterexercise2;

public class ninth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int integer;
        for(int i=1;i<=8;i++){
            
            for(int j=1;j<=8-i;j++){
                System.out.print("    ");
            }
            for(int j=1;j<=i;j++){
                integer=(int)Math.pow(2, j-1);
                System.out.printf("%4d",integer);
            }
            for(int k=i-1;k>=1;k--){
                integer=(int)Math.pow(2, k-1);
                System.out.printf("%4d",integer);
            }
            
            
        System.out.println();
        }
    }    

}

//exercise 4-20
package fourthchapterexercise3;

public class first {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        System.out.println("prime of 2 to 1000 is:");
        int count=0;
        
        for(int i=2;i<=1000;i++){
            boolean isprime=true;
            
            for(int j=2;j<=i/2;j++){
                if(i%j==0){
                    isprime=false;
                    break;
                }
            }
            
            if(isprime){
                count++;
                System.out.printf("%4d",i);
            }
            
            if(count%8==0&&isprime)
                System.out.println();
        }
    }

}


//exercise 4.21
package fourthchapterexercise3;
import java.util.Scanner;
//This function is not a rigorous
//The corrected
public class second {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        Scanner in=new Scanner(System.in);
        
        System.out.print("please input loan amount:");
        int loanamount=in.nextInt();
        
        System.out.print("Number of years:");
        int numberofyears=in.nextInt();
        double interestrate=0.05;
        int count;
        System.out.println("Inerest Rate      Monthly payment       Total Payment");
        
        //computational
        for(count=0;count<=24;count++){
            
            double monthlyinterestrate=interestrate/12;
            
            //The monthly payment
            double monthlypayment=(loanamount*monthlyinterestrate)/
                    (1-1/Math.pow(1+monthlyinterestrate,numberofyears*12));
            
            //total payment
            double totalpayment=monthlypayment*12*numberofyears;
            
            System.out.println((int)(interestrate*100000)/1000.0+"%\t\t  "+
            (int)(monthlypayment*100)/100.0+"0\t\t"+(int)(totalpayment*100)/100.0);
            
            interestrate +=0.00125;
        }
    }

}


//exercise 4.22
package fourthchapterexercise3;
import java.util.Scanner;
public class third {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        Scanner in=new Scanner(System.in);
        
        System.out.print("Loan Amount:");
        int loanamount=in.nextInt();
        
        System.out.print("Number of Years:");
        int numberofyears=in.nextInt();
        
        System.out.print("Annual Interest rate:");
        double annualinterestrate=in.nextDouble();
        
        double monthlyinterestrate=annualinterestrate/12;
        double monthlypayment=(loanamount*monthlyinterestrate)/
                (1-1/Math.pow(1+monthlyinterestrate,numberofyears*12));
        double totalpayment=monthlypayment*12*numberofyears;
        
        System.out.println("\nMonthly Payment:"+monthlypayment);
        System.out.println("Total Payment"+totalpayment);
        System.out.println();
        
        double interest=0,principal;
        double balance=loanamount;
        System.out.println("Payment\t\tInterest\t\t        Principal\t\t        Balance");
        for(int i=1;i<=numberofyears*12;i++){
            interest=monthlyinterestrate*balance;
            principal=monthlypayment-interest;
            balance=balance-principal;
            System.out.println(i+"\t\t"+interest+"\t\t"+principal+"\t\t"+balance);
        }
    }

}


//exercise 4.23
package fourthchapterexercise3;

public class fourth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double sum=0;
        for(int i=1;i<=5000;i++){
            sum += 1.0/i;
        }
        System.out.println("This is from left to right:"+sum);
        
        sum=0;
        for(int i=5000;i>=1;i--){
            sum += 1.0/i;
        }
        System.out.println("This is from right to left:"+sum);
    }

}


//exercise 4.24
package fourthchapterexercise3;

public class fifth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double sum=0;
        double molecular=1;
        double denominator=3;
        
        for(int i=1;i<=49;i++){
            sum += molecular/denominator;
            molecular += 2;
            denominator += 2;
        }
        System.out.println("result is "+sum);
    }

}


//exercise 4.25
package fourthchapterexercise3;
public class sixth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for(int i=10000;i<=100000;i += 10000){
            double pi=0,sum=0;
            for (int j=0;j<=i;j++){
                sum =sum+Math.pow(-1,j)*(1.0/(2*j+1));
            }
            pi=4*sum;
            System.out.print("when i="+i+",pi="+pi+"\n");
        }
    }

}


//exercise 4.26
package fourthchapterexercise3;

//The arithmetic is not good enough
public class seventh {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for(int i=10000;i<=100000;i +=10000){
            double sum=1;
            double generaltype=1;
            for(int j=1;j<=i;j++){
                for(int k=1;k<=j;k++){
                    generaltype *= 1.0/k;
                }
                sum += generaltype;
            }
            System.out.println("When i="+i+",e="+sum);
        }
        
    }

}


//exercise 4.27
package fourthchapterexercise3;

public class eighth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int count=0;
        System.out.println("A leap year all in twenty-first Century is:");
        for(int year=2001;year<=2100;year++){
            if(year%4==0&&year%100!=0||year%400==0){
                System.out.print(year+" ");
                count++;
                if(count%10==0)
                    System.out.println();
            }
        }
    }

}


//exercise 4.28
package fourthchapterexercise3;
import java.util.Scanner;
public class ninth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input year and days of week:");
        int year=in.nextInt();
        int january=in.nextInt();
        
        //The calculation of the first day of the month is the day of the week
        int february=(january+31)%7;
        int march=(february+28)%7;
        if(year%4==0&&year%100!=0||year%400==0)
            march=(february+29)%7;
        
        int april=(march+31)%7;
        int may=(april+30)%7;
        int june=(may+31)%7;
        int july=(june+30)%7;
        int august=(july+31)%7;
        int september=(august+31)%7;
        int october=(september+30)%7;
        int november=(october+31)%7;
        int december=(november+30)%7;
        
        //matching week
        String week=null;
        
        switch(january){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("January 1, "+year+" is "+week);
        
        switch(february){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("february 1, "+year+" is "+week);
        
        switch(march){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("march 1, "+year+" is "+week);
        
        switch(april){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("april 1, "+year+" is "+week);
        
        switch(may){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("may 1, "+year+" is "+week);
        
        switch(june){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("june 1, "+year+" is "+week);
        
        switch(july){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("july 1, "+year+" is "+week);
        
        switch(august){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("august 1, "+year+" is "+week);
        
        switch(september){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("september 1, "+year+" is "+week);
        
        switch(october){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("october 1, "+year+" is "+week);
        
        switch(november){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("november 1, "+year+" is "+week);
        
        switch(december){
        case 0:
            week="Sunday";
            break;
        case 1:
            week="Monday";
            break;
        case 2:
            week="Tuesday";
            break;
        case 3:
            week="Wednesday";
            break;
        case 4:
            week="Thursday";
            break;
        case 5:
            week="Friday";
            break;
        case 6:
            week="Saterday";
            break;
        default:
            break;
        }
        System.out.println("december 1, "+year+" is "+week);
    }

}


//exercise 4.29
package fourthchapterexercise3;
import java.util.Scanner;
public class tenth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        
        System.out.print("please input year and days of week:");
        int year=in.nextInt();
        int january=in.nextInt();
        
        //The calculation of the first day of the month is the day of the week
        int february=(january+31)%7;
        int march=(february+28)%7;
        if(year%4==0&&year%100!=0||year%400==0)
            march=(february+29)%7;
        
        int april=(march+31)%7;
        int may=(april+30)%7;
        int june=(may+31)%7;
        int july=(june+30)%7;
        int august=(july+31)%7;
        int september=(august+31)%7;
        int october=(september+30)%7;
        int november=(october+31)%7;
        int december=(november+30)%7;
        
        //January
        System.out.println("\t\t     January"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        int count=1;
        for(int i=0;i<january;i++){
            System.out.print("   \t");
        }
        
        //wrap
        int temp=january;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //February
        System.out.println("\t\t     February"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<february;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=february;
        
        //A month has 28 or 29 days
        int feb=28;
        if(year%4==0&&year%100!=0||year%400==0)
            feb=29;
        for(count=1;count<=feb;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //March
        System.out.println("\t\t     March"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<march;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=march;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //April
        System.out.println("\t\t     April"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<april;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=april;
        
        //A month has 30 days
        for(count=1;count<=30;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //May
        System.out.println("\t\t     May"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<may;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=may;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //June
        System.out.println("\t\t     June"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<june;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=june;
        
        //A month has 30 days
        for(count=1;count<=30;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //July
        System.out.println("\t\t     July"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<july;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=july;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //August
        System.out.println("\t\t     August"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<august;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=august;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //September
        System.out.println("\t\t     September"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<september;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=september;
        
        //A month has 30 days
        for(count=1;count<=30;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //October
        System.out.println("\t\t     October"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<october;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=october;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //November
        System.out.println("\t\t     November"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<november;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=november;
        
        //A month has 30 days
        for(count=1;count<=30;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
        
        
        //December
        System.out.println("\t\t     December"+year+" \t");
        System.out.println("----------------------------------------------------");
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        count=1;
        for(int i=0;i<december;i++){
            System.out.print("   \t");
        }
        
        //wrap
        temp=december;
        
        //A month has 31 days
        for(count=1;count<=31;count++){
            if(temp%7==0){
                System.out.println();
                temp=0;
            }
            System.out.printf("%3d\t",count);
            temp++;
        }
        System.out.println("\n");
    }

}


//exercise 4.30
package fourthchapterexercise4;
import java.util.Scanner;
public class first {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input money and annual interest rate and number of month:");
        double monthlymoney=in.nextDouble();
        double yearlyinterestrate=in.nextDouble();
        double numberofmonth=in.nextDouble();
        
        double monthlyinterestrate=yearlyinterestrate/12;
        double sum=0;
        for(int i=1;i<=numberofmonth;i++){
            sum=(monthlymoney+sum)*(1+monthlyinterestrate);
        }
        System.out.print(numberofmonth+"months later,the money on account of "+sum);
    }

}


//exercise 4.31
package fourthchapterexercise4;
import java.util.Scanner;
public class second {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("Enter the initial deposit amount:");
        double sum=in.nextDouble();
        System.out.print("Enter annual percentage yiekd:");
        double yearlyinterestrate=in.nextDouble();
        System.out.print("Enter maturityperiod(number if months):");
        double numberofmonth=in.nextDouble();
        
        double monthlyinterestrate=yearlyinterestrate/1200;
        System.out.println("Month\t\tCD Value");
        for(int i=1;i<=numberofmonth;i++){
            sum=sum*(1+monthlyinterestrate);
            System.out.printf("%5d",i);
            System.out.println("\t\t"+sum);
        }
    }

}

//exercise 4.32
package fourthchapterexercise4;

import java.util.Scanner;

public class third {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int lottery=0;
        
        //Generate an integer, the number of two integers is different
        while (true){
            lottery=(int)(Math.random()*90+10);
            int first=lottery/10;
            int second=lottery%10;
            if(first!=second)
                break;
        }
        
        Scanner in=new Scanner(System.in);
        
        System.out.print("Enter your lottery pick (two digits):");
        int guess =in.nextInt();
        
        //separation lottery digit
        int lotteryDigit1=lottery/10;
        int lotteryDigit2=lottery%10;
        
        //separation guess digit
        int guessDigit1=guess/10;
        int guessDigit2=guess%10;
        
        System.out.println("The lottery number is "+lottery);
        
        //judge
        if (guess == lottery)
            System.out.println("Exact match:you win $10000");
        else if(guessDigit2==lotteryDigit1&&guessDigit1==lotteryDigit2)
            System.out.println("Match all digits: you win $3000");
        else if(guessDigit1==lotteryDigit1
                ||guessDigit1==lotteryDigit2
                ||guessDigit2==lotteryDigit1
                ||guessDigit2==lotteryDigit2)
            System.out.println("Match one digit:you win $ 1000");
        else
            System.out.println("Sorry,no match");
    }

}


//exercise 4.33
package fourthchapterexercise4;

public class fourth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.print("Ten thousand the following numbers,perfect number:");
        for(int i=1;i<=10000;i++){
            int sum=0;
            for (int j=1;j<i;j++){
                if(i%j==0){
                    sum=sum+j;
                }
            }
            if(sum==i){
                System.out.print(i+" ");
            }
        }
    }

}


//exercise 4.34
package fourthchapterexercise4;

import java.util.Scanner;

public class fifth {

    public static void main(String[] args) {
        
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        
        int computercount=0;
        int personcount=0;
        while (true){
            System.out.print("scissor(0),rock(1),paper(2):");
            int input=in.nextInt();
            
            int computer=(int)(Math.random()*3);
            
            if(computer==0&&input==1){
                System.out.println("The computer is scissor.You are rock.You win");
                personcount++;
                computercount=0;
            }
            else if (computer==0&&input==2){
                System.out.println("The computer is scissor.You are paper.You lost.");
                computercount++;
                personcount=0;
            }
                
            else if (computer==0&&input==0){
                System.out.println("The computer is scissor.You are scissor.It is a draw.");
                computercount=0;
                personcount=0;
            }
                
            
            else if (computer==1&&input==0){
                System.out.println("The computer is rock.You are scissor.You lost.");
                computercount++;
                personcount=0;
            }
                
            else if (computer==1&&input==1){
                System.out.println("The computer is rock.You are rock.It is a draw.");
                computercount=0;
                personcount=0;
            }
                
            else if (computer==1&&input==2){
                System.out.println("The computer is rock.You are paper.You win.");
                personcount++;
                computer=0;
            }
                
            
            else if (computer==2&&input==0){
                System.out.println("The computer is paper.You are scissor.You win.");
                personcount++;
                computercount=0;
            }
                
            else if (computer==2&&input==1){
                System.out.println("The computer is paper.You are rock.You lost.");
                computercount++;
                personcount=0;
            }
                
            else if (computer==2&&input==2){
                System.out.println("The computer is paper.You are paper.It is a draw.");
                computercount=0;
                personcount=0;
            }
            
            if(computercount==2){
                System.out.println("The computer won two times.");
                break;
            }
            if(personcount==2){
                System.out.println("You won two times.");
                break;
            }
    
        }
    }
}


//exercise 4.35
package fourthchapterexercise4;

public class sixth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double sum=0;
        for(int i=1;i<=624;i++){
            sum += 1/(Math.pow(i, 0.5)+Math.pow(i+1,0.5));
        }
        System.out.print("sum is "+sum);
    }

}


//exercise 4.37
package fourthchapterexercise4;

import java.util.Scanner;

public class seventh {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("input a integer(Decimal system):");
        int integer=in.nextInt();
        int count=0;
        int temp=integer;
        String number="";
        
        //求出字符变成二进制后的长度
        while (integer!=0 ){
            int remainder=integer%2;
            integer /=2;
            number =number+(char)(remainder+48);
            count++;
        }
        
        //转换在数组中
        int newcount=count;
        char a[]=new char[count];
        while (temp!=0 ){
            int remainder=temp%2;
            temp /=2;
            a[count-1]=(char)(remainder+48);
            count--;
        }
        
        
        for(int i=0;i<newcount;i++){
            System.out.print(a[i]);
        }
        System.out.print("\n"+number);
    }

}


//exercise 4.38
package fourthchapterexercise4;
import java.util.Scanner;
public class eight {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("please input integer(Decimal system):");
        int integer=in.nextInt();
        
        String hexadecimal="";
        while(integer!=0){
            int temp=integer%16;
            if(temp<=9&&temp>=0)
                hexadecimal=(char)(temp+‘0‘)+hexadecimal;
            else 
                hexadecimal=(char)(temp-10+‘A‘)+hexadecimal;
            integer=integer/16;
        }
        
        System.out.println("The hexadecimal is "+hexadecimal);
    }

}


//exercise 4.39
package fourthchapterexercise4;

public class ninth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double sum=0;
        for(int i=0;i<=5000;i++){
            sum=5000+i*0.08;
            if(sum>=30000){
                System.out.println("minimum sales is "+(i-1));
                System.exit(0);
            }
        }
        
        
        for(int i=5000;i<=10000;i++    ){
            sum=5000+5000*0.08+i*0.10;
            if(sum>30000){
                System.out.println("minimum sales is "+(i-1));
                System.exit(0);
            }
        }
        int i=10000;
        
        
        while (sum<30000){
            sum=5000+5000*0.08+10000*0.10+i*0.12;
            i++;
        }
        
        System.out.println("minimum sales is "+(i-1));
        System.exit(0);
    }

}

//exercise 4.40
package fourthchapterexercise4;

public class tenth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int positive=0;
        int negative=0;
        for(int i=1;i<=1000000;i++){
            int temp=(int)(Math.random()*2);
            if(temp==0)
                positive++;
            else 
                negative++;
        }
        System.out.println("The positive is "+positive);
        System.out.println("The negative is "+negative);
    }

}


//exercise 4.41
package fourthchapterexercise5;
import java.util.Scanner;
public class first {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("Enter numbers: ");
        int integer=in.nextInt();
        int max=0;
        int count=0;
        while (integer!=0){
            if(max<integer){
                max=integer;
                count=0;
            }
            if(max==integer){
                count++;
            }
            integer=in.nextInt();
        }
        
        System.out.println("The large number is "+max);
        System.out.println("The occurrence count of the largest number is "+count);
        
    }

}


//exercise 4.43
package fourthchapterexercise5;
import java.util.Scanner;
public class second {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("Enter the number of second :");
        int seconds=in.nextInt();
        while(true){
            
            try {  
                //pause for a second
                Thread.sleep(1000);  
                
                if((seconds-1)==0){
                System.out.println("Stopped");
                break;
                }
                if((seconds-1)==1){
                    System.out.println((seconds-1)+" second remaining");
                    seconds--;
                    continue;
                }
                System.out.println((seconds-1)+" seconds remaining");
                
                seconds--;
                
            //format    
            } catch (InterruptedException e) {  
                //If abnormal, the output to the console
                e.printStackTrace();  
            }
            
                        
        }
        
    }

}



//exercise 4.44
package fourthchapterexercise5;

import java.util.Scanner;

public class third {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        
        int count=0;
        
        for(int i=1;i<=1000000;i++){
            double x=Math.random()*2-1;
            double y=Math.random()*2-1;
            
            double distance1=Math.pow((x*x+y*y), 0.5);
            double distance2=Math.pow((x-1)*(x-1)+(y-1)*(y-1),0.5);
            
            if(distance1>distance2&&x>0&&y>0)
                count++;
            if(x<0)
                count++;
        }
        
        double chance=count/1000000.0;
        System.out.println("The chance is "+(int)(chance*10000)/100.0+"%");
    }

}

//exercise 4.45
package fourthchapterexercise5;

public class fourth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int count=0;
        for(int i=1;i<=7;i++){
            for(int j=1;j<=7;j++){
                if(i!=j){
                    System.out.println(i+" "+j);
                    count++;
                }
            }
        }
        System.out.println("The numbers of combination is "+count);
    }

}


//exercise 4.46
package fourthchapterexercise5;
import java.util.Scanner;
public class fifth {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("Enter an integer:");
        int integer =in.nextInt();
        
        //Judgment is a positive or negative number
        boolean judge=false;
        if(integer<0){
            integer=-integer;
            judge=true;
        }
        
        //Convert decimal number to a binary number
        int count=0;
        String decimal="";
        while(integer!=0){
            int temp=integer%2;
            decimal=(char)(temp+‘0‘)+decimal;
            integer=integer/2;
            count++;
        }
        
        for(int i=1;i<=16-count;i++){
            decimal=‘0‘+decimal;
        }
        
        //Judgment is a positive or negative number
        if(judge){
            char []decimalarr=decimal.toCharArray();
            for(int i=0;i<decimalarr.length;i++){
                if(decimalarr[i]==‘0‘)
                    decimalarr[i]=‘1‘;
                else
                    decimalarr[i]=‘0‘;
            }
            for(int i=decimalarr.length-1;i>=0;i--){
                if(decimalarr[i]==‘1‘){
                    decimalarr[i]=‘0‘;
                }
                else{
                    decimalarr[i]=‘1‘;
                    break;
                }
            }
            System.out.print("The bits are ");
            for(int i=0;i<decimalarr.length;i++){
                System.out.print(decimalarr[i]);
            }
        }
        else
            System.out.println("The bits are "+decimal);
        
        
    }

}