Java Object Hash hashCode(Object obj)

Description

Returns a hash code for obj .

License

Apache License

Parameter

Parameter	Description
obj	The object to get a hash code for. May be an array or <code>null</code>.

Return

A hash code of obj or 0 if obj is null

Declaration

public static int hashCode(Object obj) 

Method Source Code

//package com.java2s;
/**//from w  w w  .  ja  va2 s  .co  m
 * Copyright 2009-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (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
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

import java.util.Arrays;

public class Main {
    /**
     * Returns a hash code for {@code obj}.
     * 
     * @param obj The object to get a hash code for. May be an array or <code>null</code>.
     * @return A hash code of {@code obj} or 0 if {@code obj} is <code>null</code>
     */
    public static int hashCode(Object obj) {
        if (obj == null) {
            // for consistency with Arrays#hashCode() and Objects#hashCode()
            return 0;
        }
        final Class<?> clazz = obj.getClass();
        if (!clazz.isArray()) {
            return obj.hashCode();
        }
        final Class<?> componentType = clazz.getComponentType();
        if (long.class.equals(componentType)) {
            return Arrays.hashCode((long[]) obj);
        } else if (int.class.equals(componentType)) {
            return Arrays.hashCode((int[]) obj);
        } else if (short.class.equals(componentType)) {
            return Arrays.hashCode((short[]) obj);
        } else if (char.class.equals(componentType)) {
            return Arrays.hashCode((char[]) obj);
        } else if (byte.class.equals(componentType)) {
            return Arrays.hashCode((byte[]) obj);
        } else if (boolean.class.equals(componentType)) {
            return Arrays.hashCode((boolean[]) obj);
        } else if (float.class.equals(componentType)) {
            return Arrays.hashCode((float[]) obj);
        } else if (double.class.equals(componentType)) {
            return Arrays.hashCode((double[]) obj);
        } else {
            return Arrays.hashCode((Object[]) obj);
        }
    }

    /**
     * Compares two objects. Returns <code>true</code> if
     * <ul>
     * <li>{@code thisObj} and {@code thatObj} are both <code>null</code></li>
     * <li>{@code thisObj} and {@code thatObj} are instances of the same type and
     * {@link Object#equals(Object)} returns <code>true</code></li>
     * <li>{@code thisObj} and {@code thatObj} are arrays with the same component type and equals()
     * method of {@link Arrays} returns <code>true</code> (not deepEquals())</li>
     * </ul>
     * 
     * @param thisObj The left hand object to compare. May be an array or <code>null</code>
     * @param thatObj The right hand object to compare. May be an array or <code>null</code>
     * @return <code>true</code> if two objects are equal; <code>false</code> otherwise.
     */
    public static boolean equals(Object thisObj, Object thatObj) {
        if (thisObj == null) {
            return thatObj == null;
        } else if (thatObj == null) {
            return false;
        }
        final Class<?> clazz = thisObj.getClass();
        if (!clazz.equals(thatObj.getClass())) {
            return false;
        }
        if (!clazz.isArray()) {
            return thisObj.equals(thatObj);
        }
        final Class<?> componentType = clazz.getComponentType();
        if (long.class.equals(componentType)) {
            return Arrays.equals((long[]) thisObj, (long[]) thatObj);
        } else if (int.class.equals(componentType)) {
            return Arrays.equals((int[]) thisObj, (int[]) thatObj);
        } else if (short.class.equals(componentType)) {
            return Arrays.equals((short[]) thisObj, (short[]) thatObj);
        } else if (char.class.equals(componentType)) {
            return Arrays.equals((char[]) thisObj, (char[]) thatObj);
        } else if (byte.class.equals(componentType)) {
            return Arrays.equals((byte[]) thisObj, (byte[]) thatObj);
        } else if (boolean.class.equals(componentType)) {
            return Arrays.equals((boolean[]) thisObj, (boolean[]) thatObj);
        } else if (float.class.equals(componentType)) {
            return Arrays.equals((float[]) thisObj, (float[]) thatObj);
        } else if (double.class.equals(componentType)) {
            return Arrays.equals((double[]) thisObj, (double[]) thatObj);
        } else {
            return Arrays.equals((Object[]) thisObj, (Object[]) thatObj);
        }
    }
}

Related

1. hash(Object... values)
2. hashCode(final Object o)
3. hashCode(final Object... objects)
4. hashCode(final Object... objects)
5. hashCode(Object o)
6. hashCode(Object obj)
7. hashCode(Object object)
8. hashCode(Object... args)
9. hashCode(Object... objects)