当我清楚地覆盖相等方法时，我似乎无法弄清楚为什么我总是变得真实

问题描述

我正在尝试解决这个问题，但似乎无法正确比较。

当我在运行时尝试设置代码时，结果最终会在我需要它生成错误测试时变为 True。广泛的测试表明它总是正确的，我不知道如何在它上面产生错误。

import java.util.Scanner;

public class LandTract
{
    // instance variables
    private static double length,width,area;

    /**
     * Constructor for objects of class LandTract
     */
    public LandTract(double length,double width,double area)
    {
        // initialise instance variables
        length = 0;
        width = 0;
    }

    public LandTract(double length,double width)
    {
        this.length = length;
        this.width = width;
    }
    
    public void setLength(double length)
    {
        this.length = length;
    }
    
    public double getLength()
    {
        return length;
    }
    
    public void setWidth(double width)
    {
        this.width = width;
    }
    
    public double getWidth()
    {
        return width;
    }
    
    public double getArea()
    {
        return area = length * width;
    }
    
    public String toString()
    {
        String str = "Length: " + length + "\nWidth: " + width;
        return str;
    }
    
    public boolean equals(Object obj)
    {
        LandTract land = (LandTract) obj;
        if (this.length != land.length)
            return false;
        if (this.width != land.width)
            return false;
        if (this.area != land.area)
            return false;
        
            return true;
    }
    
    public static void main(String[] args)
    {
        Scanner key = new Scanner(system.in);
        
        System.out.print("Enter the length of the first tract of land: ");
        length = key.nextDouble();
        key.nextLine();
        System.out.print("Enter the width of the first tract of land: ");
        width = key.nextDouble();
        key.nextLine();
        LandTract land1 = new LandTract(length,width);
        System.out.println("The area of the first tract of land is " + land1.getArea());
        System.out.println();
        
        System.out.print("Enter the length of the second tract of land: ");
        length = key.nextDouble();
        key.nextLine();
        System.out.print("Enter the width of the second tract of land: ");
        width = key.nextDouble();
        key.nextLine();
        LandTract land2 = new LandTract(length,width);
        System.out.println("The area of the second tract of land is " + land2.getArea());
        System.out.println();
        
        if (land1.equals(land2))
            System.out.println("Both tracts of land are the same size.");
        else
            System.out.println("They are different sizes.");
    }
}

解决方法

令人困惑且具有讽刺意味的错误评论的最佳示例：

// instance variables
private static double length,width,area;

---

当您：

1. （真的）引入实例变量：

   private double length,area;
   

2. 修复 main 方法中的编译器问题（通过声明具有相同标识符的局部变量......没有好的风格但很快）：

   public static void main(String[] args) {
      double length,width;
      // ...
   }