标签：
http://bbs.csdn.net/topics/390000725
总结：
equals在没重写之前和==一样，重写之后，equals只要内容一样即为true
equals跟==一般情况下是等价的，但是对于String类型，它重写了equals方法，比较的是内容。默认情况下两个都是比较的引用地址，除非你重写equals方法。
equals源码：
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; }
版主解答：
“但是经常说==两边对象是按地址在比较，而equals()是按内容在比较”这句话在排除根类Object以及没有自己重写equals方法的情况下是对的。
即Object类中equals的实现就是用的==
其他继承Object的equals方法基本上都重写了这个方法，比如String类的equals方法：
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equalspublic boolean equals(Object anObject)Compares this string to the specified object. The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object. Overrides:equals in class ObjectParameters:anObject - The object to compare this String against Returns:true if the given object represents a String equivalent to this string, false otherwiseSee Also:compareTo(String), equalsIgnoreCase(String) |
这是String的equals方法源码：
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public boolean equals(Object obj) { if(this == obj) return true; if(obj instanceof String) { String s = (String)obj; int i = count; if(i == s.count) { char ac[] = value; char ac1[] = s.value; int j = offset; int k = s.offset; while(i-- != 0) if(ac[j++] != ac1[k++]) return false; return true; } } return false; } |
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原文地址：http://www.cnblogs.com/kenshinobiy/p/4652040.html
