java - 我在调用矩形面积的方法时遇到问题

Question

我的 Rectangle 类上有 getter 和 setter、默认和重载的构造函数、toString 和区域方法。我的 RectangleTest 只是我的值和输出语句。我一直在尝试让我的面积方法正常工作，但无论我尝试什么，都没有调用我的高度和宽度。

public class Rectangle {
public double width ;
private double height; 
private String color ;
private double area;

public double getWidth ( ) { return width; }
public void setWidth ( double w ) {
this.width = w; } 
public double getHeight ( ) {return height; }
public void setHeight ( double h ) { 
this.height = h; } 

public String getColor ( ) {return color; }

public void setColor ( String co ) { 
this.color = (co); } 

public Rectangle ( ) { 
height = 0;
width = 0;
color = (" ");
System.out.println("Default constructor");
//default constructor
}

public Rectangle ( double w, double h, String co) { 
width = w;
height = h;
color = (co);
System.out.println("Overloaded constructor" );
//overloaded constructor
} 
public double findArea (){
return area;
}
public void setArea (double width, double height){
area = width * height;   
}
public String toString ( ) {
String x = "Rectangle width is " + width + ", height is " + height +
    ", color is " + color + " and the area is " + area;
return x;
} 
}

public class RectangleTest {


public static void main(String[] args) {

Rectangle shape = new Rectangle(2.0, 4.0, "red");
Rectangle r2 = new Rectangle(2.0, 3.0, "Yellow");
Rectangle r3 = new Rectangle(2.0, 3.0, "Yellow");


do { r2.width++  ; 

} while (r2.width == (r3.width));

if (r2.equals (r3))
    System.out.println("r2 still equals r3" );
else
    System.out.println("r2 is now a square");

    System.out.println("First rectangle is " + shape );

    System.out.println("Second rectangle is " + r2 );

if (r2.equals (r3))
    System.out.println("\nShape 2 equals shape 3");
else
    System.out.println("\nShape 2 and 3 are not equal");

//System.exit(0);
}
}

Answer 1

findArea 是一个可计算的结果，这意味着它的结果是基于计算其他值的结果。根据您的代码示例，计算 area 的唯一位置是在调用 setArea 时，但从未调用 setArea。

更好的解决方案是让 findArea 自行执行计算

public double findArea (){
    return width * height;
}

这样做的好处是，您不必在 width 或 height 发生变化时记住调用 setArea 方法