if语句

if选择结构

顺序结构

package struct;

public class Domeshunxu {
    public static void main(String[] args) {
        System.out.println("hello1");
        System.out.println("hello2");
        System.out.println("hello3");
        System.out.println("hello4");
        System.out.println("hello5");
    }
}

if多选结构

package struct;

import java.lang.reflect.GenericDeclaration;
import java.util.Scanner;

public class domexuanze {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入内容；");
        String a=scanner.nextLine();

        //判断字符串是否想等equals
        if (a.equals("chen")){
            System.out.println(a);
        }
        System.out.println("end");


        scanner.close();
    }
}

双向选择

package struct;

import com.sun.deploy.security.SelectableSecurityManager;

import java.util.Scanner;

public class xuangxuanze {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩");
        int i=scanner.nextInt();

        if (i>60){
            System.out.println("成绩合格");
        

        }else{
            System.out.println("成绩不合格");
        }

scanner.close();
    }
}

if多选择结构

package struct;

import java.util.Scanner;

public class Domeif {
    public static void main(String[] args) {
        System.out.println("输入成绩");
        Scanner scanner = new Scanner(System.in);
        int d = scanner.nextInt();
        if (d==100){
            System.out.println("manfen");
        }else if (d<100 && d>=80){
            System.out.println("youxiu");
        }else if (d<80 && d>=60){
            System.out.println("yiban");
        }else{
            System.out.println("cha");
        }
        scanner.close();
    }
}

嵌套的if语句

int d = scanner.nextInt();
if (d==100){
    System.out.println("manfen");
}else if (d<100 && d>=80){
    if (d<90 && d>=80){
        System.out.println("棒");
    }else {
    }System.out.println("youxiu");