package de.intevation.gnv.math;

import java.io.Serializable;

/**
 * Tuple (i, j) to model a pair of integers. Useful to store index pairs
 * in maps.
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 */
public class IJKey
implements   Serializable
{
    /**
     * i component of the tuple.
     */
    public int i;
    /**
     * j component of the tuple.
     */
    public int j;

    /**
     * Default constructor.
     */
    public IJKey() {
    }

    /**
     * Constructor to set i and j.
     * @param i The i component.
     * @param j The j component.
     */
    public IJKey(int i, int j) {
        this.i = i;
        this.j = j;
    }

    /**
     * Orders i and j by their values.
     */
    public void sort() {
        if (i > j) {
            int t = i;
            i = j;
            j = t;
        }
    }

    /**
     * Hashes i and j into a common value.
     * @return the hash code.
     */
    @Override
    public int hashCode() {
        return (i << 16) | j;
    }

    /**
     * IJKeys are considered equal if the i and j components
     * are equal.
     * @param obj The other IJKey
     * @return true if the IJKeys are equal else false.
     */
    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof IJKey)) {
            return false;
        }
        IJKey other = (IJKey)obj;
        return i == other.i && j == other.j;
    }
}
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