Java tutorial
//package com.java2s; import java.util.HashMap; import java.util.Iterator; public class Main { public static Object keyString(HashMap<String, String> map, String o) { Iterator<String> it = map.keySet().iterator(); while (it.hasNext()) { Object keyString = it.next(); if (map.get(keyString).equals(o)) return keyString; } return null; } }