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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equals
public 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 Object
Parameters:
anObject - The object to compare this String against
Returns:
true if the given object represents a String equivalent to this string, false otherwise
See Also:
compareTo(String), equalsIgnoreCase(String)
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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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