/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package com.alibaba.citrus.util.internal.apache.lang;
/**
* <p>
* 从Apache commons-lang中的同名类简化而得。
* </p>
* <p>
* Assists in implementing {@link Object#hashCode()} methods.
* </p>
* <p>
* This class enables a good <code>hashCode</code> method to be built for any
* class. It follows the rules laid out in the book <a
* href="http://java.sun.com/docs/books/effective/index.html">Effective Java</a>
* by Joshua Bloch. Writing a good <code>hashCode</code> method is actually
* quite difficult. This class aims to simplify the process.
* </p>
* <p>
* All relevant fields from the object should be included in the
* <code>hashCode</code> method. Derived fields may be excluded. In general, any
* field used in the <code>equals</code> method must be used in the
* <code>hashCode</code> method.
* </p>
* <p>
* To use this class write code as follows:
* </p>
* <p/>
* <pre>
* public class Person {
* String name;
* int age;
* boolean smoker;
* ...
*
* public int hashCode() {
* // you pick a hard-coded, randomly chosen, non-zero, odd number
* // ideally different for each class
* return new HashCodeBuilder(17, 37).
* append(name).
* append(age).
* append(smoker).
* toHashCode();
* }
* }
* </pre>
* <p>
* If required, the superclass <code>hashCode()</code> can be added using
* {@link #appendSuper}.
* </p>
*
* @author Stephen Colebourne
* @author Gary Gregory
* @author Pete Gieser
*/
public class HashCodeBuilder {
/** Constant to use in building the hashCode. */
private final int iConstant;
/** Running total of the hashCode. */
private int iTotal = 0;
/**
* <p>
* Uses two hard coded choices for the constants needed to build a
* <code>hashCode</code>.
* </p>
*/
public HashCodeBuilder() {
iConstant = 37;
iTotal = 17;
}
/**
* <p>
* Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
* these should be different for each class, however this is not vital.
* </p>
* <p>
* Prime numbers are preferred, especially for the multiplier.
* </p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial
* value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the
* multiplier
* @throws IllegalArgumentException if the number is zero or even
*/
public HashCodeBuilder(int initialNonZeroOddNumber, int multiplierNonZeroOddNumber) {
if (initialNonZeroOddNumber == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires a non zero initial value");
}
if (initialNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires an odd initial value");
}
if (multiplierNonZeroOddNumber == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires a non zero multiplier");
}
if (multiplierNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires an odd multiplier");
}
iConstant = multiplierNonZeroOddNumber;
iTotal = initialNonZeroOddNumber;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>boolean</code>.
* </p>
* <p>
* This adds <code>iConstant * 1</code> to the <code>hashCode</code> and not
* a <code>1231</code> or <code>1237</code> as done in java.lang.Boolean.
* This is in accordance with the <quote>Effective Java</quote> design.
* </p>
*
* @param value the boolean to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(boolean value) {
iTotal = iTotal * iConstant + (value ? 0 : 1);
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>boolean</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(boolean[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (boolean element : array) {
append(element);
}
}
return this;
}
// -------------------------------------------------------------------------
/**
* <p>
* Append a <code>hashCode</code> for a <code>byte</code>.
* </p>
*
* @param value the byte to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(byte value) {
iTotal = iTotal * iConstant + value;
return this;
}
// -------------------------------------------------------------------------
/**
* <p>
* Append a <code>hashCode</code> for a <code>byte</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(byte[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (byte element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>char</code>.
* </p>
*
* @param value the char to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(char value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>char</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(char[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (char element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>double</code>.
* </p>
*
* @param value the double to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(double value) {
return append(Double.doubleToLongBits(value));
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>double</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(double[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (double element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>float</code>.
* </p>
*
* @param value the float to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(float value) {
iTotal = iTotal * iConstant + Float.floatToIntBits(value);
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>float</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(float[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (float element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>int</code>.
* </p>
*
* @param value the int to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(int value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>int</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(int[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>long</code>.
* </p>
*
* @param value the long to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(long value) {
iTotal = iTotal * iConstant + (int) (value ^ value >> 32);
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>long</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(long[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (long element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>Object</code>.
* </p>
*
* @param object the Object to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(Object object) {
if (object == null) {
iTotal = iTotal * iConstant;
} else {
if (object.getClass().isArray() == false) {
// the simple case, not an array, just the element
iTotal = iTotal * iConstant + object.hashCode();
} else {
// 'Switch' on type of array, to dispatch to the correct handler
// This handles multi dimensional arrays
if (object instanceof long[]) {
append((long[]) object);
} else if (object instanceof int[]) {
append((int[]) object);
} else if (object instanceof short[]) {
append((short[]) object);
} else if (object instanceof char[]) {
append((char[]) object);
} else if (object instanceof byte[]) {
append((byte[]) object);
} else if (object instanceof double[]) {
append((double[]) object);
} else if (object instanceof float[]) {
append((float[]) object);
} else if (object instanceof boolean[]) {
append((boolean[]) object);
} else {
// Not an array of primitives
append((Object[]) object);
}
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>Object</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(Object[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (Object element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>short</code>.
* </p>
*
* @param value the short to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(short value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>short</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(short[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (short element : array) {
append(element);
}
}
return this;
}
/**
* <p>
* Adds the result of super.hashCode() to this builder.
* </p>
*
* @param superHashCode the result of calling <code>super.hashCode()</code>
* @return this HashCodeBuilder, used to chain calls.
* @since 2.0
*/
public HashCodeBuilder appendSuper(int superHashCode) {
iTotal = iTotal * iConstant + superHashCode;
return this;
}
/**
* <p>
* Return the computed <code>hashCode</code>.
* </p>
*
* @return <code>hashCode</code> based on the fields appended
*/
public int toHashCode() {
return iTotal;
}
}