Java tutorial
import java.util.Map; import java.util.WeakHashMap; public class Main { public static void main(String[] args) { WeakHashMap<String, String> weakHashMap = new WeakHashMap<String, String>(); weakHashMap.put("1", "first"); weakHashMap.put("2", "two"); weakHashMap.put("3", "from java2s.com"); // check existence of value for key 2 System.out.println("Checking value for key 2"); System.out.println(weakHashMap.get("2")); } }