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JVM如何处理对对象的引用，然后使用new关键字将其设置为新的对象值

[英]How does JVM handle references to an object that is then set to a new object value using new keyword

原文 2015-06-23 00:43:24 2 1 java/ pointers/ jvm

I'm curious about what happens to java object references that are passed through a method param, set to a class scoped variable in the class where the method lives, and then the original object passed as a param is set to a new value using the new keyword. 我很好奇通过方法参数传递的java对象引用会发生什么，将其设置为方法所在的类中的类范围变量，然后将使用param传递的原始对象设置为使用新关键字。

My understanding is that objects are passed by reference not value in method params, but what happens in the case when the original object is set to a new value using = new? 我的理解是，对象是通过引用传递的，而不是方法参数中的值，但是当使用= new将原始对象设置为新值时会发生什么呢？ Does java create a new location in memory for this new object so that pointers to the existing object remain in tact? Java是否会在内存中为此新对象创建一个新位置，以使指向现有对象的指针保持原样？

Hope I'm not asking a dumb question. 希望我不要问一个愚蠢的问题。 - Duncan -邓肯

1 个解决方案

You can't pass Objects and you can't set Objects. 您不能传递对象，也不能设置对象。

You only have primitives and references. 您只有原语和引用。

A references is an address, typically a 4-byte value like an int 引用是地址，通常是4字节的值，例如int

So when you change a reference it is no different to setting an int value to something else. 因此，当您更改引用时，将int值设置为其他值没有什么不同。 In fact, setting a reference to null can be exactly the same as setting an int to 0 实际上，将引用设置为null可以与将int设置为0完全相同。

Does java create a new location in memory for this new object so that pointers to the existing object remain in tact? Java是否会在内存中为此新对象创建一个新位置，以使指向现有对象的指针保持原样？

When you create a new object, new memory is always used. 创建新对象时，始终使用新内存。 This will happen even if the old object no longer used anywhere else. 即使旧对象不再在其他任何地方使用，也会发生这种情况。