新整数与 valueOf
我使用 Sonar 来使我的代码更清晰，它指出我正在使用 新的 Integer(1) 而不是 Integer.valueOf(1).因为似乎 valueOf 没有实例化一个新对象，所以对内存更友好.valueOf 如何不实例化一个新对象?它是如何工作的?对所有整数都是这样吗?
I was using Sonar to make my code cleaner, and it pointed out that I'm using new Integer(1) instead of Integer.valueOf(1). Because it seems that valueOf does not instantiate a new object so is more memory-friendly. How can valueOf not instantiate a new object? How does it work? Is this true for all integers?
推荐答案
Integer.valueOf 为 -128 到 +127 的值实现缓存代码>.请参阅 Java 语言规范的最后一段，第 5.1.7 节，它解释了装箱的要求(通常根据 .valueOf 方法实现).
Integer.valueOf implements a cache for the values -128 to +127. See the last paragraph of the Java Language Specification, section 5.1.7, which explains the requirements for boxing (usually implemented in terms of the .valueOf methods).
http:///docs.oracle.com/javase/specs/jls/se7/html/jls-5.html#jls-5.1.7
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