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package com.jchanghong.core.builder;
import java.io.Serializable;
/**
* Wrap an identity key (System.identityHashCode()) so that an object can only be equal() to itself.
*
* This is necessary to disambiguate the occasional duplicate identityHashCodes that can occur.
*
* TODO 待整理
* 来自于Apache-Commons-Lang3
* @author looly，Apache-Commons
* @since 4.2.2
*/
final class IDKey implements Serializable{
private static final long serialVersionUID = 1L;
private final Object value;
private final int id;
/**
* Constructor for IDKey
*
* @param _value The value
*/
public IDKey(final Object _value) {
// This is the Object hashcode
id = System.identityHashCode(_value);
// There have been some cases (LANG-459) that return the
// same identity hash code for different objects. So
// the value is also added to disambiguate these cases.
value = _value;
}
/**
* returns hashcode - i.e. the system identity hashcode.
*
* @return the hashcode
*/
@Override
public int hashCode() {
return id;
}
/**
* checks if instances are equal
*
* @param other The other object to compare to
* @return if the instances are for the same object
*/
@Override
public boolean equals(final Object other) {
if (!(other instanceof IDKey)) {
return false;
}
final IDKey idKey = (IDKey) other;
if (id != idKey.id) {
return false;
}
// Note that identity equals is used.
return value == idKey.value;
}
}