java.lang.Comparable Maven / Gradle / Ivy

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 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
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 */

package java.lang;

/**
 * This interface should be implemented by all classes that wish to define a
 * natural order of their instances.
 * {@link java.util.Collections#sort} and {@code java.util.Arrays#sort} can then
 * be used to automatically sort lists of classes that implement this interface.
 * 
 * The order rule must be both transitive (if {@code x.compareTo(y) < 0} and
 * {@code y.compareTo(z) < 0}, then {@code x.compareTo(z) < 0} must hold) and
 * invertible (the sign of the result of x.compareTo(y) must be equal to the
 * negation of the sign of the result of y.compareTo(x) for all combinations of
 * x and y).
 * 
 * In addition, it is recommended (but not required) that if and only if the
 * result of x.compareTo(y) is zero, then the result of x.equals(y) should be
 * {@code true}.
 */
public interface Comparable {

    /**
     * Compares this object to the specified object to determine their relative
     * order.
     *
     * @param another
     *            the object to compare to this instance.
     * @return a negative integer if this instance is less than {@code another};
     *         a positive integer if this instance is greater than
     *         {@code another}; 0 if this instance has the same order as
     *         {@code another}.
     * @throws ClassCastException
     *             if {@code another} cannot be converted into something
     *             comparable to {@code this} instance.
     */
    int compareTo(T another);
}