《Java技术》第一次作业

（一）学习总结

1.在java中通过Scanner类完成控制台的输入，查阅JDK帮助文档，Scanner类实现基本数据输入的方法是什么？不能只用文字描述，一定要写代码，通过具体实例加以说明。

import java.util.*;

public class ABC {
    public static void main(String[] args) {
            int a;
            Scanner input = new Scanner(System.in);
            a = input.nextInt();
            System.out.println(a);
}

这就是输入一个int型的数，如果想要输入一个double型的数就把next后面的int改成double。如果要输入一个字符串，next后面就不用写东西。

2.Random类和Math类的random()方法都能产生随机数，这两种方式有什么区别，各有什么特点呢？查阅JDK帮助文档，并举例加以说明。
Math类：int x=(int)(Math.random()*x+y); 就是产生一个x-y之间的数。
Random类：
Random rand = new Random();
int x=rand.nextInt(x)+y;
就是产生一个x-y之间的数。

3.运行下列程序，结果是什么？查阅资料，分析为什么。
输出结果是不等于0.3，因为在计算double类型数据时会产生误差。
比较两个double类型的数据相等时，看二者相减是否无限趋近于0.

public class ABC {
    public static void main(String args[]) { 
        double a = 0.1;
        double b = 0.1;
        double c = 0.1;
        if((a + b + c)-0.3<1e-6){
            System.out.println("等于0.3");
        }else {
            System.out.println("不等于0.3");
        }
    }     
}

（二）实验总结

实验内容：
1.看商品猜价格

import java.util.*;

public class ABC {
    public static void main(String[] args) {
        int x = 0, a = 0, i = 0, j = 0, k = 0, n = 0;
        String t;
        Scanner input = new Scanner(System.in);
        ww: while (true) {
            x = (int) (Math.random() * 100);
            k = 100;
            for (i = 5; i > 0; i--) {
                System.out.println("请输入商品价格，还有" + i + "次机会");
                a = input.nextInt();
                if (a == x) {
                    System.out.println("猜对了");
                    j += k;
                    break;
                }
                if (a > x) {
                    System.out.println("猜大了");
                    k -= 20;
                }
                if (a < x) {
                    System.out.println("猜小了");
                    k -= 20;
                }
                if (i == 1) {
                    System.out.println("正确答案是" + x);
                }
            }
            n++;
            System.out.println("是否进行下一轮？输入yes进行下一轮，输入no退出游戏");
            while (true) {
                t = input.next();
                if (t.equals("yes")) {
                    System.out.println("进行下一轮");
                    break;
                } else if (t.equals("no")) {
                    System.out.println("退出游戏");
                    break ww;
                } else {
                    System.out.println("输入错误，请重新输入");
                }
            }
        }
        System.out.println("一共猜了" + n + "次，总得分为" + j);
    }
}

2.万年历

import java.util.*;

public class ABC {

    public static void main(String[] args) {
        int year, year1, month, sum, sum1, sum2, i, n, zong = 0, h = 0;
        Scanner input = new Scanner(System.in);
        while (true) {
            System.out.println("请输入年份");
            year = input.nextInt();
            System.out.println("请输入月份");
            month = input.nextInt();
            if (year < 1900 || month < 1 || month > 12) {
                System.out.println("输入错误，请重新输入");
            } else {
                break;
            }
        }
        sum1 = 0;
        sum2 = 0;
        year1 = year;
        for (year1 = year1 - 1; year1 >= 1900; year1--) {
            if (year1 % 4 == 0 && year1 % 100 != 0 || year1 % 400 == 0) {
                sum1 = sum1 + 366;
            } else {
                sum1 = sum1 + 365;
            }
        }

        for (i = 1; i < month; i++) {
            if (i == 1 || i == 3 || i == 5 || i == 7 || i == 8 || i == 10 || i == 12) {
                sum2 = sum2 + 31;
            } else if (i == 4 || i == 6 || i == 9 || i == 11) {
                sum2 = sum2 + 30;
            } else if (i == 2) {
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    sum2 = sum2 + 29;
                } else {
                    sum2 = sum2 + 28;
                }
            }
        }
        sum = sum1 + sum2;
        System.out.println("星期日\t星期一\t星期二\t星期三\t星期四\t星期五\t星期六");
        switch (sum % 7) {
        case 0:
            System.out.print("\t");
            h = 2;
            break;
        case 1:
            System.out.print("\t\t");
            h = 3;
            break;
        case 2:
            System.out.print("\t\t\t");
            h = 4;
            break;
        case 3:
            System.out.print("\t\t\t\t");
            h = 5;
            break;
        case 4:
            System.out.print("\t\t\t\t\t");
            h = 6;
            break;
        case 5:
            System.out.print("\t\t\t\t\t\t");
            h = 7;
            break;
        case 6:
            h = 1;
            break;
        }
        if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
            zong = 31;
        } else if (month == 4 || month == 6 || month == 9 || month == 11) {
            zong = 30;
        } else if (month == 2) {
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                zong = 29;
            }

            else {
                zong = 28;
            }
        }

        for (n = 1; n <= zong; n++, h++) {
            System.out.print(n + "\t");
            if (h % 7 == 0) {
                System.out.println(" ");
            }
        }

    }
}

3.评分系统

import java.util.*;

public class ABC {

    public static void main(String[] args) {
        int a[][] = new int[5][10];
        int b[][] = new int[5][8];
        int i = 0, j = 0, k = 0, t = 0;
        double n, x, y;
        double c[] = new double[5];
        int d[] = new int[5];
        Scanner input = new Scanner(System.in);
        for (i = 0; i <= 4; i++) {
            for (j = 0; j <= 9; j++) {
                System.out.println("请第" + (j + 1) + "位评委给第" + (i + 1) + "号选手打分");
                a[i][j] = input.nextInt();
            }
        }
        for (i = 0; i <= 4; i++) {
            for (j = 0; j <= 9; j++) {
                for (k = 0; k <= 8; k++) {
                    if (a[i][k] > a[i][k + 1]) {
                        t = a[i][k];
                        a[i][k] = a[i][k + 1];
                        a[i][k + 1] = t;
                    }
                }
            }
        }
        for (i = 0; i <= 4; i++) {
            for (j = 0; j <= 7; j++) {
                b[i][j] = a[i][j + 1];
            }
        }
        for (i = 0; i <= 4; i++) {
            n = 0;
            x = 0;
            for (j = 0; j <= 7; j++) {
                n++;
                x += b[i][j];
            }
            c[i] = x / n;
            d[i] = i + 1;
        }
        for (i = 0; i <= 4; i++) {
            for (k = 0; k <= 3; k++) {
                if (c[k] < c[k + 1]) {
                    y = c[k];
                    c[k] = c[k + 1];
                    c[k + 1] = y;
                    t = d[k];
                    d[k] = d[k + 1];
                    d[k + 1] = t;
                }
            }
        }
        for (i = 0; i <= 4; i++) {
            System.out.println("第" + (i + 1) + "名是第" + d[i] + "号选手，得分为" + c[i]);
        }
    }
}