How can I create a memory leak in Java?

Question

I just had an interview, and I was asked to create a memory leak with Java.

Needless to say, I felt pretty dumb having no clue on how to eve

Answer 1

I thought it was interesting that no one used the internal class examples. If you have an internal class; it inherently maintains a reference to the containing class. Of course it is not technically a memory leak because Java WILL eventually clean it up; but this can cause classes to hang around longer than anticipated.

public class Example1 {
  public Example2 getNewExample2() {
    return this.new Example2();
  }
  public class Example2 {
    public Example2() {}
  }
}

Now if you call Example1 and get an Example2 discarding Example1, you will inherently still have a link to an Example1 object.

public class Referencer {
  public static Example2 GetAnExample2() {
    Example1 ex = new Example1();
    return ex.getNewExample2();
  }

  public static void main(String[] args) {
    Example2 ex = Referencer.GetAnExample2();
    // As long as ex is reachable; Example1 will always remain in memory.
  }
}

I've also heard a rumor that if you have a variable that exists for longer than a specific amount of time; Java assumes that it will always exist and will actually never try to clean it up if cannot be reached in code anymore. But that is completely unverified.