java的字符串拼接

 

每当我用+运算符拼接字符串时, 总有人跟我提出你应该用StringBuffer.

我真的希望提建议的人先看看String类的源代码, 从JavaSE6开始, 通过+运算符拼接字符串就是用StringBuilder或者StringBuffer类和他们的append()方法来实现的.

 

原话如下:

From java.lang.String source code:

 

The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method. String conversions are implemented through the method toString, defined by Object and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele, The Java Language Specification.

 

 

但是, 这种实现只是依赖于Javac的语法糖解析的, 编译后的class代码对于字符串+的拼接并没有做优化,

所以执行效率上将, 语法糖解析后的+拼接的代码依然达不到StringBuilder或者StringBuffer那样的速度.

具体讨论可以参考这篇帖子的讨论:

http://www.iteye.com/topic/1040986

 

所以具体到实际情况时:

对于需要大量使用的字符串拼接的情况(比如在循环中), 最好使用StringBuilder或者StringBuffer.

否则可以直接使用+以方便阅读.