顺序结构

if选择结构

if单选结构

package com.he.struct;

import java.util.Scanner;

public class IfDemo1 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入内容");
        String s=scanner.nextLine();
        //equals判断字符串是否相等
        if (s.equals("Hello")){
            System.out.println(s);
        }
        System.out.println("End");
        scanner.close();
    }
}

if else结构

package com.he.struct;

import java.util.Scanner;

public class IfDemo2 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入成绩");
        int score=scanner.nextInt();
        if (score>60){
            System.out.println("及格");
        }else {
            System.out.println("不及格");
        }
        scanner.close();
    }
}

if else if结构

package com.he.struct;

import java.util.Scanner;

public class IfDemo3 {
    public static void main(String[] args) {
        //判断分数的等级
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入成绩");
        int score=scanner.nextInt();

        if (score==100){
            System.out.println("恭喜满分");
        }else if(score<100 && score>=90){
            System.out.println("A级");
        }else if(score<90 && score>=80){
            System.out.println("B级");
        }else if(score<80 && score>=70){
            System.out.println("C级");
        }else if(score<70 && score>=60){
            System.out.println("D级");
        }else if(score<60 && score>=0){
            System.out.println("不及格");
        }else {
            System.out.println("成绩不合法");
        }
        scanner.close();
    }
}