Java包装器类真的是不可变的吗? [英] Are Java wrapper classes really immutable?

问题描述

Java包装器类应该是不可变的.这意味着一旦创建了对象，例如

Java Wrapper classes are supposed to be immutable. This means that once an object is being created, e.g.,

Integer i = new Integer(5);

其值不能更改.但是，做

its value cannot be changed. However, doing

i = 6;

是完全有效的.

那么，在这种情况下，不变性是什么意思?这与自动装箱/拆箱有关吗?如果是这样，有什么办法可以防止编译器执行此操作?

So, what does immutability in this context mean? Does this have to do with auto-boxing/unboxing? If so, is there any way to prevent the compiler from doing it?

谢谢

推荐答案

i 是参考.您的代码将引用 i 更改为指向另一个相同的，不变的 Integer .

i is a reference. Your code change the reference i to point to a different, equally immutable, Integer.

final Integer i = Integer.valueOf(5);

可能会更有用.

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