更新时间:2022-08-23 14:00:12
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) |
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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