Garbage Collection

[Milan Sutaria]

Source: Enthuware

    How many objects will be eligible for GC just after the method returns? 
 

public void compute(Object p)
{
 Object a = new Object();
 int x = 100;
 String str = "abc";
}
  

Answer: Objects passed to the method are never garbage collected in that method. So p cannot be GCed.
x is not an object.
"abc" is a string literal which goes to the string pool and is not GCed.
So, only a is eligible for GC.

1> even after the method returns the string literal isn't GCed?
2> what if i explicitly assign null to str: str=null; ?

[Justin Smith]

Hi Sutaria,

The reason why strings are not GCed is because, String will be handled in a different way than all the other Objects. Even though String IS-A Object, the memory handling of Strings are different. This is called String Pool. Before even creating a new String Literal say for example
"Sutaria" in the pool, it will check for the existance of the string. If it can't find one then it will create. So lets come your question

1) Even after the method returns, the string literal won't be GCed.

This is because the String pooling

2) If you create String s=null;
This will not create a String Object at all (unless you mention String s = "null" .This is because you have just given a reference 's' and not actually created an Object.

Hope this clarifies your doubt...

[Milan Sutaria]

Justin,
i meant adding a line to the end of the code: str=null;

[Raphael Rabadan]

Originally posted by Milan Sutaria:
Justin,
i meant adding a line to the end of the code: str=null;

Literal's will only be GCed if the class is unloaded from the JVM. A way to make it GCed is initializing it with new String("") like this..:

public void compute(Object p) {
Object a = new Object();
int x = 100;
String str = new String("abc");
}

With this code you'll have two objects to be GCed.

[Milan Sutaria]

thanks Raphael