Garbage Collection - Java

Question

Can someone please tell me how the garbage collection works using this example. The question is how many objects are eligible for garbage collection at the specified point in the program.

interface Animal {
void makeNoise();
}

class Horse implements Animal {
    Long weight = 1200L;
    public void makeNoise() {

        System.out.println("whinny");
   }
}

public class Icelandic extends Horse {
    public void makeNoise() {
        System.out.println("vinny");
    }

    public static void main(String[] args) {
        Icelandic i1 = new Icelandic();
        Icelandic i2 = new Icelandic();
        Icelandic i3 = new Icelandic();
        i3 = i1;
        i1 = i2;
        i2 = null;
        i3 = i1;
//**here**
    }
}

Answer 1

• Objects become eligible for garbage collection when they are not reachable. Their reachability is explained in the following link.

You can try this link to understand how objects become eligible for garbage collection and they start drawing diagram for your own. If you face problems, let us know.

Answer 2

Just took it from your code. Just follow the code and you will be good.

        Icelandic i1 = new Icelandic();  // i1 = firstObject --> Location XXXX
        Icelandic i2 = new Icelandic();  // i2 = secondObject --> Location YYYY
        Icelandic i3 = new Icelandic();  // i3 = thirdObject  ---> Location ZZZZ

        i3 = i1;
        // HERE i3 = i1; i3 --> XXXX; i1 --> XXXX; i2 --> YYYY  
        (ZZZZ No reference)

         i1 = i2;
        // Here i1 --> YYYY; i2 --> YYYY; i3 --> XXXX

        i2 = null;
        // Here i2 --> null; i1-->YYYY; i3 --> XXXX

        i3 = i1;
        // Here i1-->YYYY; i2 --> NULL; i3--> YYYY 
       (No reference for XXXX and ZZZZ)

Hope this helps.

Note, Long weight is also an Object. So total of 4 objects eligible for GC. Let me know if it helped.