import java.util.Scanner;

class Tools
{
    final static int START_TAX = 2000;
    double tax;

    public double computeTax(double wage)
    {
        if (wage - START_TAX <= 0)
        {
            tax = 0;
        }
        if (wage - START_TAX <= 500)
        {
            tax = (wage - 2000) * 0.05;

        }
        if ((wage - START_TAX > 500) && (wage - START_TAX <= 2000))
        {
            tax = (wage - 2000) * 0.1 - 25;
        }
        if (wage - START_TAX > 2000)
        {
            tax = (wage - 2000) * 0.15 - 125;
        }
        return tax;// 把大括号里面的return语句去掉，直接在外面return。
    }
}

public class Salary
{
    String employeeId = "";
    double wage = 0;
    static double tax = 0;
    double realWage = 0;

    public double computeTax()
    {
        tax = new Tools().computeTax(wage);// 这里没必要把此函数设置为static的。
        return tax;
    }

    public double computeRealWage()
    {
        realWage = wage - this.computeTax();
        return realWage;
    }

    public static void main(String[] args)
    {
        Salary salary = new Salary();
        Scanner sc = new Scanner(System.in);
        System.out.println("职工号");
        salary.employeeId = sc.nextLine();
        System.out.println("税前工资");
        salary.wage = sc.nextDouble();
        System.out.println("职工号" + salary.employeeId + "税前工资" + salary.wage
                + "扣税" + salary.computeTax() + "实发    工资"
                + salary.computeRealWage());
    }
}

------解决方案--------------------
静态属性和方法只能被静态到代码块访问，在非静态到代码块中访问静态到方法当然不行了，你可以将被调用的方法设置成静态的

------解决方案--------------------
如果必须要这样调用的话，得这样。供楼主参考
Java code

import java.util.Scanner;

class Tools
{
    final static int START_TAX = 2000;
    private static double tax;//这里要设置为static 

    public static double computeTax(double wage) ////这里也要设置为static 
    {
        if (wage - START_TAX <= 0)
        {
            tax = 0;
        }
        if (wage - START_TAX <= 500)
        {
            tax = (wage - 2000) * 0.05;

        }
        if ((wage - START_TAX > 500) && (wage - START_TAX <= 2000))
        {
            tax = (wage - 2000) * 0.1 - 25;
        }
        if (wage - START_TAX > 2000)
        {
            tax = (wage - 2000) * 0.15 - 125;
        }
        return tax;
    }
}

public class Salary
{
    String employeeId = "";
    double wage = 0;
    static double tax = 0;
    double realWage = 0;

    public double computeTax()
    {
        tax =Tools.computeTax(wage);
        return tax;
    }

    public double computeRealWage()
    {
        realWage = wage - this.computeTax();
        return realWage;
    }

    public static void main(String[] args)
    {
        Salary salary = new Salary();
        Scanner sc = new Scanner(System.in);
        System.out.println("职工号");
        salary.employeeId = sc.nextLine();
        System.out.println("税前工资");
        salary.wage = sc.nextDouble();
        System.out.println("职工号" + salary.employeeId + "税前工资" + salary.wage
                + "扣税" + salary.computeTax() + "实发工资"
                + salary.computeRealWage());
    }
}

------解决方案--------------------
探讨


如果必须要这样调用的话，得这样。供楼主参考
Java code

import java.util.Scanner;

class Tools
{
    final static int START_TAX = 2000;
    private static double tax;//这里要设置为static 

    public static double computeTax(d……