Java tutorial
//package com.java2s; import java.util.*; public class Main { public static <K, V> Map<K, V> immutableMap(Map<K, V> map) { return Collections.unmodifiableMap(map); } public static <K, V> Map<K, V> immutableMap(Collection<Map.Entry<K, V>> entrySet) { Map<K, V> resultMap = new HashMap<K, V>(); for (Map.Entry<K, V> entry : entrySet) { if (entry != null) resultMap.put(entry.getKey(), entry.getValue()); } return Collections.unmodifiableMap(resultMap); } }