Memory leak generation example in Java

gistfile1.java

import java.util.HashMap;
import java.util.Map;
 
public class MemoryLeak {
 
  public static void main(String[] args) {
    Map<Key, String> map = new HashMap<Key, String>(1000);   
    int counter = 0;
    while (true) {
       // creates duplicate objects due to bad Key class
      map.put(new Key("dummyKey"), "value");
      counter++;
      if (counter % 1000 == 0) {
        System.out.println("Map size: " + map.size());
        System.out.println("Free memory after count " + counter
         + " is " + getFreeMemory() + "MB");       
        sleep(1000);
      }     
    }
  }
 
  // inner class key without hashcode() or equals() 
  // bad implementation causes memory leak
  static class Key {
    private String key; 
    public Key(String key) {
      this.key = key;
    } 
  }
 
  public static void sleep(long sleepFor) {
    try {
      Thread.sleep(sleepFor);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
 
  public static long getFreeMemory() {
    return Runtime.getRuntime().freeMemory() / (1024 * 1024);
  }
 
}

/**
  static class Key {
    private String key; 
    public Key(String key) {
      this.key = key;
    }
    @Override
    public boolean equals(Object obj) { 
      if (obj instanceof Key) {
        return key.equals(((Key) obj).key);
      } else {
        return false;
      } 
    }
 
    @Override
    public int hashCode() {
      return key.hashCode();
    }
  }
*/