难道真的没人能解释吗???

Question

有main方法的那个类必须是public的

Answer 1

import java.awt.*;class Point {
    private int x = 0;
    private int y = 0;    public Point() {    }
    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }
    public boolean equals(Object o) {
        if (!(o instanceof Point))return false;
        Point p = (Point)o;
        return p.x == x && p.y == y;
    }
}class ColorPoint extends Point {
    private Point point;
    private Color color;
    public ColorPoint(int x, int y, Color color) {
        point = new Point(x, y);
        this.color = color;
    }
    public Point asPoint() {
        return point;
    }
    public boolean equals(Object o) {
        if (!(o instanceof ColorPoint))return false;
        ColorPoint cp = (ColorPoint)o;
        return cp.point.equals(point) && cp.color.equals(color);
    }
}class PointTest{
    public static void main(String[] str){
        Point p=new Point(1,2);
        ColorPoint cp1=new ColorPoint(1,2,Color.RED);
        ColorPoint cp2=new ColorPoint(1,2,Color.BLUE);
        System.out.println(cp1.equals(p));
        System.out.println(p.equals(cp1));
        System.out.println(p.equals(cp2));
        System.out.println(cp1.equals(cp2));
    }
}自己看看

Answer 2

可以编译啊，我在dos下面直接编译是可以的啊
只不过编译不过而已
呵呵！

Answer 3

class Point {
    private final int x;  // private int x;
    private final int y;  // private int y; 你试一下
    
    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }    
    public boolean equals(Object o) {
        if (!(o instanceof Point))return false;
        Point p = (Point)o;
        return p.x == x && p.y == y;
    }
}

Answer 4

是因为我将Point类曾经单独编译了一次,导致当前目录里有了Point.class,从而导致错误的调用,换到一个空目录一切ok,谢谢各位,结贴!!