Garbage collection of String literals

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If a string is defined as literal at compile time [e.g: String str = "java";] then will it be garbage collected?

Probably not. The code objects will contain one or more references to the String objects that represent the literals. So as long as the code objects are reachable, the String objects will be to.

It is possible for code objects to become unreachable, but only if they were dynamically loaded … and their classloader is destroyed.

If I use the intern method [e.g: String str = new String("java").intern()] then will it be garbage collected?

The object returned by the intern call will be the same object that represents the "java" string literal. (The "java" literal is interned at class loading time. When you then intern the newly constructed String object in your code snippet, it will lookup and return the previously interned "java" string.)

However, interned strings that are not identical with string literals can be garbage collected once they become unreachable. The PermGen space is garbage collected on all recent HotSpot JVMs. (Prior to Java 8 … which drops PermGen entirely.)

Also will it be treated differently from string literal in point 1.

No … because it is the same object as the string literal.

And indeed, once you understand what is going on, it is clear that string literals are not treated specially either. It is just an application of the “reachability” rule …

Some places it is mentioned that literals will be garbage collected only when String class will be unloaded? Does it make sense because I don’t think the String class will ever be unloaded.

You are right. It doesn’t make sense. The sources that said that are incorrect. (It would be helpful if you posted a URL so that we can read what they are saying for ourselves …)

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