Question

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.

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

My code:

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;
}

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;
    }

}

Answer 1

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.