不变对象，可变对象，equals和==

原来一直对equals和==有点晕。

今天突然想到把java类库的源码找出来看看。呵呵，全清楚了。

java.lang.Object类的equals()定义是：

??? public boolean equals(Object obj) {
??????? return (this == obj);
??? }

而java.lang.String类覆盖了父类的equals()，定义如下：

??? public boolean equals(Object anObject) {
??????? if (this == anObject) {
??????????? return true;
??????? }
??????? if (anObject instanceof String) {
??????????? String anotherString = (String)anObject;
??????????? int n = count;
??????????? if (n == anotherString.count) {
??????????????? char v1[] = value;
??????????????? char v2[] = anotherString.value;
??????????????? int i = offset;
??????????????? int j = anotherString.offset;
??????????????? while (n-- != 0) {
??????????????????? if (v1[i++] != v2[j++])
??????????????????? return false;
??????????????? }
?????????????? return true;
??????????? }
??????? }
??? return false;
??? }

其中，??? /** The value is used for character storage. */
??? private char value[];

??? /** The offset is the first index of the storage that is used. */
??? private int offset;

??? /** The count is the number of characters in the String. */
??? private int count;

看过后是不是很清楚啊hehe。

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