Java HashMap get 有效，但 containsKey 无效 [英] Java HashMap get works but containsKey does not

问题描述

我正在尝试在 HashMap 中找到一个键.我可以使用 'get' 打印选定的键，但是当我在 if 语句中使用 'containsKey' 时，找不到它.

I am trying to locate a key in a HashMap. I can print the selected key by using 'get' but when I use 'containsKey' in an if statement, it is not found.

我知道密钥存在于地图中，但它一直返回错误.有什么想法吗?

I KNOW the key is present in the Map but it keeps returning false. Any ideas people?

我的代码:

public static boolean checkLowerStructuralSupport(Location location) {

    boolean hasSupport = false;

    Location supportingLocation = new Location(location.getX(), location.getY(), location.getZ() - 1);

    System.out.println(_levels.get(supportingLocation.getZ()).getLevelSites2().get(supportingLocation)); //works

    if (_levels.get(supportingLocation.getZ()).getLevelSites2().containsKey(supportingLocation)) {
        hasSupport = true;
    } else {
        hasSupport = false;
    }

    return hasSupport;
}

这是 Location 类的代码:

Here is the code for the Location class:

public class Location {

    protected int _x;
    protected int _y;
    protected int _z;

    public Location(int xAxis, int yAxis, int zAxis) {
        this._x = xAxis;
        this._y = yAxis;
        this._z = zAxis;
    }

    public void equals() {
        //not implemented yet
    }

    public void HashCode() {
        //not implemented yet
    }

    public String toString() {
        String locationString = Integer.toString(_x) + Integer.toString(_y) + Integer.toString(_z);
        return locationString;
    }

    public void setX(int XAxis) {
        this._x = XAxis;
    }

    public int getX() {
        return this._x;
    }

    public void setY(int YAxis) {
        this._y = YAxis;
    }

    public int getY() {
        return this._y;
    }

    public void setZ(int ZAxis) {
        this._z = ZAxis;
    }

    public int getZ() {
        return this._z;
    }

}

推荐答案

您必须确保 Location 类已正确实现其 hashCode() 和 equals(对象) 方法(文档).也就是说，如果两个 Location 对象实际上是相等的，它们应该共享一个公共哈希码，并且它们的 equals 方法应该返回 true.

You must ensure that the Location class has properly implemented its hashCode() and equals(Object) methods (documentation). That is, if two Location objects are effectively equal, they should share a common hash code and their equals method should return true.

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