Java流程控制-if和switch

Java流程控制-if和switch

if

• If (boolean表达式) {为true,执行这里的} else

package opearater;

import java.util.Scanner;

public class SuanYuanYunSuanFu {
    public static void main(String[] args) {
        int HaoGanDu = 90;
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入你对我的好感度：0-100");
        while (scanner.hasNextInt()) {
            HaoGanDu = scanner.nextInt();
//            System.out.println(HaoGanDu > 80 ? "我喜欢你" : "我对你没感觉");
            if (HaoGanDu >= 99){
                System.out.println("我爱你");
            }else if(HaoGanDu >= 90  ){
                System.out.println("我特别喜欢你");
            }else if (HaoGanDu>=80){
                System.out.println("我喜欢你");
        }else if (HaoGanDu >= 40){
                System.out.println("我对你没感觉");}
            else {
                System.out.println("我讨厌你");
            }
//            scanner.close();
            }
//        scanner.close();

        }
}

switch

• 记得加break语句，防止case穿透

package opearater;

import java.util.Scanner;

public class Switch {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请写下你对我的感觉");
        while (scanner.hasNextLine()){
            String feeling = scanner.nextLine();
            switch (feeling){
                case "我爱你":
                    System.out.println("好感度>=99");
                    break;
                case "我特别喜欢你":
                    System.out.println("好感度>90");
                    break;
                case "我喜欢你":
                    System.out.println("好感度>80");
                    break;
                case "我讨厌你":
                    System.out.println("好感度<20");
                    break;
                default:
                    System.out.println("我对你没感觉");


            }
        }

    }
}

• 将生成的class文件拖入Idea，从得到的反编译文件可知switch(字符串)也是转化为switch(数字)处理的

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package opearater;

import java.util.Scanner;

public class Switch {
    public Switch() {
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请写下你对我的感觉");

        while(scanner.hasNextLine()) {
            String feeling = scanner.nextLine();
            byte var4 = -1;
            switch(feeling.hashCode()) {
            case -877105257:
                if (feeling.equals("我特别喜欢你")) {
                    var4 = 1;
                }
                break;
            case 25052448:
                if (feeling.equals("我爱你")) {
                    var4 = 0;
                }
                break;
            case 769834857:
                if (feeling.equals("我喜欢你")) {
                    var4 = 2;
                }
                break;
            case 782944075:
                if (feeling.equals("我讨厌你")) {
                    var4 = 3;
                }
            }

            switch(var4) {
            case 0:
                System.out.println("好感度>=99");
                break;
            case 1:
                System.out.println("好感度>90");
                break;
            case 2:
                System.out.println("好感度>80");
                break;
            case 3:
                System.out.println("好感度<20");
                break;
            default:
                System.out.println("我对你没感觉");
            }
        }

    }
}