Java tutorial
//package com.java2s; import java.util.*; public class Main { public static <T> Set removeRepetition(Collection<T> ts) { if (ts == null || ts.isEmpty()) { return Collections.emptySet(); } Map<T, Object> map = new LinkedHashMap(); for (T t : ts) { if (!map.containsKey(t)) { map.put(t, -1); } } Set<T> set = map.keySet(); return set; } }