import java.util.Iterator;
import java.util.Map;
import java.util.WeakHashMap;
public class Main {
public static void main(String[] argv) throws Exception {
Map weakMap = new WeakHashMap();
Object keyObject = "";
Object valueObject = "";
weakMap.put(keyObject, valueObject);
Iterator it = weakMap.keySet().iterator();
while (it.hasNext()) {
Object key = it.next();
}
}
}