Question

我目前正面临一个问题，无法找到方法。这是问题......

完成以下Point类：

public class Point{
  private int x;
  private int y;
  public Point(int x, int y){
    this.x = x;
    this.y = y;
  }
}

以下代码产生以下输出：

public class TestClass{
  public static void testEqual(Point p1, Point p2){
    if (p1.equals(p2)){
      System.out.println("The two points are equal\n"+p1);
    }else{
      System.out.println("The two points are not equal");
      System.out.println("First Point: "+ p1);
      System.out.println("Second Point: " + p2);
    }
  }
  public static void main(String [] args){
    Point p1 = new Point(2,3);
    Point p2 = Point.clonePoint(p1);
    Point p3 = new Point(1,1);
    Point p4 = new Point(2,3);
    testEqual(p1,p2);
    testEqual(p1,p3);
    testEqual(p1,p4);
    testEqual(p2,p4);
  }
}

输出

The two points are equal
The X Coordinate is 2 and the Y Coordinate is 3
The two points are not equal
First Point: The X Coordinate is 2 and the Y Coordinate is 3
Second Point: The X Coordinate is 1 and the Y Coordinate is 1
The two points are equal
The X Coordinate is 2 and the Y Coordinate is 3
The two points are equal
The X Coordinate is 2 and the Y Coordinate is 3

我能理解所有的事情但除了这一行Point p2 = Point.clonePoint(p1); 我该如何解决？

Answer 1

我认为您的作业要求您向Point课程添加cloning method，如下所示：

public class Point{
  private int x;
  private int y;
  public Point(int x, int y){
    this.x = x;
    this.y = y;
  }
  public static Point clonePoint(Point p){ return new Point(p.x,p.y); }
}

Answer 2

添加get方法，将点坐标返回到Point类：

public int getX()
{
   return x;
}

public int getY()
{
   return y;
}

然后将以下clonePoint()静态方法添加到Point类：

public static Point clonePoint(Point p)
{
   return new Point(p.getX(), p.getY());
}

然后将以下equals()方法添加到Point班级：

public boolean equals(Point p)
{
   return (p.getX() == getX()) && (p.getY() == getY());
}

Answer 3

这就是你所需要的：

[注意最后一个方法'clone'是一种静态（类）方法，您可以通过在其前面加上类名“Point”后跟'。']来访问它。

public class Point {

    private int x;
    private int y;

    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public String toString() {
        return "The X Coordinate is " + x + " and the Y Coordinate is " + y;
    }

    @Override
    public boolean equals(Object otherPoint) {
        if (this == otherPoint) return true;
        if (otherPoint == null || getClass() != otherPoint.getClass()) return false;

        Point point = (Point) otherPoint;

        return x == point.x && y == point.y;
    }

    @Override
    public int hashCode() {
        int result = x;
        result = 31 * result + y;
        return result;
    }

    public static Point clonePoint(Point p) {
        return p != null ? new Point(p.x, p.y) : null;
    }
}

如何通过构造函数发送对象？

3 个答案: