java - 识别数组列表中的自定义对象

Question

我想检查对象 Ball 是否包含在 ArrayList 中。但是每次我通过循环时，结果都会给出错误的答案。但我已经将对象球放在 ArrayList 中。不能像这样完成:- someList.contains(new Point(x,y))

public class zbc {

    ArrayList<Balls> balls;
    public boolean somRandomFunction() {

        if (balls.contains(new Ball(i, j, k))) {
            System.out.println("-----------------true------------------");
            break;
        }
    }

}

public class Ball {

    private int row, col;

    // this is actually just a integer value used
    // by game to draw various distinct color
    private int color; 

    public Ball(int row, int col, int color) {
        this.row = row;
        this.col = col;
        this.color = color;
    }

    public int row() {
        return row;
    }

    public int col() {
        return col;
    }

    public int color() {
        return color;
    }

}

Answer 1

您应该在 Ball 中实现 equals。 Collection.contains 使用 equals。测试一下

boolean equals = new Ball(1,1,1).equals(new Ball(1,1,1))

它会返回错误