我的对象的 ArrayList，indexOf 问题 [英] ArrayList of my objects, indexOf problem

问题描述

我对 Java 的 ArrayList 有问题.我创建了一个对象，它包含两个属性，x 和 y.现在我已经在我的 ArrayList 中加载了一些对象.问题是我不知道如何使用我正在搜索的 x 属性找到某个对象的索引.有没有办法做到这一点?

I have problem with Java's ArrayList. I've created an Object, that contains two attributes, x and y. Now I've loaded some object in my ArrayList. Problem is that I don't know how to find index of some object with x atribute I'm searching. Is there any way to do this?

推荐答案

这是您要找的吗?

public class Point {

private final int x;
private final int y;

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

public int getX() {
    return x;
}

public int getY() {
    return y;
}

@Override
public boolean equals(Object o) {
    return (o instanceof Point && getX() == ((Point) o).getX() && getY() == ((Point) o)
            .getY());

}

}

public class TestIndexOf {

public static void main(String[] args){
    Point p1 = new Point(10,30);
    Point p2 = new Point(20,40);
    Point p3 = new Point(50,40);
    Point p4 = new Point(60,40);
    List<Point> list = new ArrayList<Point>();
    list.add(p1);
    list.add(p2);
    list.add(p3);
    list.add(p4);
    System.out.println(list.indexOf(p3));
}

}

如果您只想搜索 x 属性，请更改 equals 方法以仅比较 x 值，例如:

If you just want to search on the x property, change the equals method to compare only the x values like:

@Override
public boolean equals(Object o) {
    return (o instanceof Point && getX() == ((Point) o).getX());

}

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