流程控制

package 选择结构;

import java.util.Scanner;
public class IfDemo {
public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    String s = sc.next();//返回 指定索引处的值。
    char c = s.charAt(0);
    if(c>=65&&c<=90)
        System.out.println("大写字母");
    else
        System.out.println("其他");
}
}

import java.util.*;
public class SwitchDemo 
{
public static void main(String [] args)
{
int num1,num2,num;
String c;
Scanner reader=new Scanner(System.in);
System.out.println("输入正整数·");
num1=reader.nextInt();
System.out.println("输入运算符");
c=reader.next();
System.out.println("输入正整数");
num2=reader.nextInt();
switch(c)
{
case"+":System.out.println("num1+num2="+(num1+num2));break;
case"-":System.out.println("num1-num2="+(num1+num2));break;
case"/":System.out.println("num1/num2="+(num1/num2));break;
case"*":System.out.println("num1*num2="+(num1*num2));break;
}
}
}

package WhileDemo;

import java.util.Scanner;

public class WhileDemo {
public static void main(String[] args) {
    int i=2,n;
    float  fac=1;
    System.out.println("请输入一个正整数");
    Scanner sc=new Scanner(System.in);
    n=sc.nextInt();
    if(n==0||n==1){
        System.out.println(1);
    }
    while(i<=n){
        fac=fac*i;
        i++;
    }
    System.out.println(fac);
}
}

package DOWhileDemo;

import java.util.Scanner;

public class DoWhileDemo {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int x=1,add=0;
        do {
            add=add+x;
            x++; // 将x的值自增
        } while (x <= n); // 循环条件
        System.out.println(add);

    }

}

package 九九乘法表;

public class MultiplicationTable {
    public static void main(String[] args) {
        for (int i = 1; i <= 9; i++) {
            System.out.println("\n");
            for (int j = 1; j <= i; j++) {
                System.out.print(i + "*" + j + "=" + i * j + "  ");
            }
        }
    }
}