如何在更改原始引用变量后再次引用Java对象

Question

I thought that this would be a good exercise for understanding a bit more about objects.

I'm trying to figure out how to reference an object again after changing the object's original reference variable.

Take the following code:

String person = "person a"; //Line 1
person = "person b";        //Line 2

Now, line 1 creates a new String object with the reference variable being person . Line 2 assigns that reference variable to another new String object. The original String object now has no reference variable.

How would I circle back and reference the original String object that is already in memory on line 1? Say, assigning the reference variable person back to the original String object? As a subsequent thought (not that I know that much about garbage collection), but is the original object eligible for garbage collection being that it does not have a reference variable anymore after line 2, and is therefore ineligible to be referenced again?

I am seeing the hashCode() method, and also the System.identityHashCode() but can't figure out how to implement it all in order to reference the original object again.

Answer 1

Line 3: person = "person a"; Java has a String intern cache. Now if it wasn't a String (or some other cached type), the answer would be you don't. Because the referecned object was eligible for garbage collection (it has no references anymore). You can validate this like,

String person = "person a"; //Line 1
System.out.println(person.hashCode());
person = "person b";        //Line 2
person = "person a";        //Line 3
System.out.println(person.hashCode());

which will display the same hashCode twice; because it's the same instance.

Answer 2

After you assign the new String

person = "person b";

The first one vanishes.. You won't be able to use it because you have lost his address.