这个题目怎么写我不太会写，薪水问题求各位大神教教我

大神教教这题怎么写？这个我不太会写，感觉没有思路啊⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯

 public static double foo(int x) {
if (x <= 3500) return 0;
if (x <= 5000) return (x - 3500) * 0.03;
if (x <= 8000) return (x - 5000) * 0.1 + 1500 * 0.03;
return (x - 8000) * 0.2 + 3000 * 0.1 + 1500 * 0.03;
}
public static void main(String[] args) 
{
    Scanner in = new Scanner(System.in);
        int x = in.nextInt();
    System.out.println(foo(x));
}

  public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            try {
                int guessNumber = sc.nextInt();
                if (guessNumber > 8000) {
                    int num1 = guessNumber - 8000;
                    int num2 = 8000 - 5000;
                    int num3 = 5000 - 3500;
                    System.out.println(num1 * 0.2 + num2 * 0.1 + num3 * 0.03);
                } else if (guessNumber < 8000 && guessNumber > 5000) {
                    int num1 = guessNumber - 5000;
                    int num2 = 5000 - 3500;
                    System.out.println(num1 * 0.1 + num2 * 0.3);
                } else if (guessNumber < 5000 && guessNumber > 3500) {
                    System.out.println((guessNumber - 3500) * 0.03);
                } else {
                    System.out.println("不交税");
                }
            } catch (InputMismatchException e) {
                System.out.println("输入金额有误");
            }
        }
    }

    新手写码，不规范请见谅
    double b = -1;
    Scanner input=new Scanner(System.in);
    System.out.println("请输入薪水：");
    double a=input.nextInt();

    if(a>0&&a<=3500){
        b=0;
    }else if(a>3500&&a<=5000){
        b=(a-3500)*0.03;
    }else if(a>5000&&a<=8000){
        b=1500*0.03+(a-5000)*0.1;
    }else if(a>8000){
        b=1500*0.03+3000*0.1+(a-8000)*0.2;
    }

    if(b==0){
        System.out.println("不交税");        
    }else{
        System.out.println("个人所得税："+b);
    }

public static double foo(int x) {
if (x <= 3500) return 0;
if (x <= 5000) return (x - 3500) * 0.03;
if (x <= 8000) return (x - 5000) * 0.1 + 1500 * 0.03;
return (x - 8000) * 0.2 + 3000 * 0.1 + 1500 * 0.03;
}
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
int x = in.nextInt();
System.out.println(foo(x));
}

新手！

import java.util.Scanner;

public class Test {

public static void main(String[] args) {

    while (true) {
        System.out.println("请输入薪水：");
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        double m = test(i);

        if (m < 0) {
            System.out.println("应交税" + 0);
        } else {

            System.out.println("应交税：" + m + " !");
        }
    }

}

public static double test(int i) {

    double m = 0;
    switch (i / 1000) {

    default:
        m = m + ((i - 8000) * 0.2);
    case 7:
        if (i < 8000) {
            m = m + ((i - 7000) * 0.1);
        } else {
            m = m + ((1000) * 0.1);
        }
    case 6:
        if (i < 7000) {
            m = m + ((i - 6000) * 0.1);
        } else {
            m = m + (1000 * 0.1);
        }
    case 5:
        if (i < 6000) {
            m = m + ((i - 5000) * 0.1);
        } else {
            m = m + (1000 * 0.1);
        }
    case 4:
        if (i < 5000) {
            m = m + ((i - 4000) * 0.03);
        } else {
            m = m + (1000 * 0.03);
        }
    case 3:
        if (i < 4000) {
            m = m + ((i - 3500) * 0.03);
        } else {
            m = m + (500 * 0.03);
        }

        break;

    }

    return m;

}

}