Java流程控制04：if选择结构

if语句

判断结构

if(是否满足条件){满足条件的执行语句}

package com.kuang.sequence;

import java.util.Scanner;

public class ifDemo01 {
    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
        //==别用来判断字符串 if(布尔表达式){如何布尔表达式为真}else{布尔表达式为假}
        if(s.equals("hello")){
            System.out.println(s);
        }
        System.out.println("End");
        scanner.close();

    }
}

选择结构

if(score<60){
    System.out.println("分数:"+score+"  不及格");
}else{
    System.out.println("分数:"+score+"  及格");
}

package com.kuang.sequence;

import java.util.Scanner;

public class ifDemo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //分数大于60分及格，小于60分为不及格
        System.out.println("请输入成绩：");
        int score = scanner.nextInt();
        if(score<60){
            System.out.println("分数:"+score+"  不及格");
        }else{
            System.out.println("分数:"+score+"  及格");
        }

        scanner.close();

    }
}

多重嵌套

if (score < 60) {
    System.out.println("分数:" + score + "  不及格");
} else if (score < 70) {
    System.out.println("分数:" + score + "  一般");
} else if(score < 90){
    System.out.println("分数:" + score + "  良好");
} else{
    System.out.println("分数:" + score + "  优秀");
}

package com.kuang.sequence;

import java.util.Scanner;

public class elseifDemo03 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //分数大于60分及格，小于60分为不及格
        System.out.println("请输入成绩：");
        int score = scanner.nextInt();

        if (score < 60) {
            System.out.println("分数:" + score + "  不及格");
        } else if (score < 70) {
            System.out.println("分数:" + score + "  一般");
        } else if(score < 90){
            System.out.println("分数:" + score + "  良好");
        } else{
            System.out.println("分数:" + score + "  优秀");
        }

        scanner.close();
    }
    }