In java what happens to an Object after a static method has returned

Question

I have an Object that occupies a large chunk of memory, I pass the object into a static helper method for processing. What does the JVM do with the Object after the method returns?

public class Helper {
    public static boolean processObject(Object object) {
        // Do something with object
        return true;
    }
}

Usage:

Object object = new Object(); // large object created
if (Helper.processObject(object)) {
    // do something
}

My concern is that the large object will stick around in memory for longer than if it was processed in the same class.

Answer 1

It will stick around as long as there is still a reference to it. Once the last reference goes out of scope it can be garbage collected (but it won't nessissary be collected immediately). I have expanded your example to more clearly demonstrate

public static void main(String[] args) {

    int[][] largeArray=new int[1000][10000]; // large object created

    use(largeArray);

    //object still retained

    while(true){

    }

}

public static void use(int[][] in){

}

This is usually fine. But you could allow it to be collected earlier by not holding on to the reference at all

public static void main(String[] args) {


    use(new int[1000][10000]);

    while(true){

    }

}

public static void use(int[][] in){

}

Equally explicitly nulling out the variable would also allow it to be collected earlier.

public static void main(String[] args) {

    int[][] largeArray=new int[1000][10000];

    use(new int[1000][10000]);

    largeArray=null;

    while(true){

    }

}

Usually this isn't worth worrying about, but if the other code is in a long loop it might be (although thats probably a sign you need to refactor your code)