Here you can find the source of copyFeatureSet(Set
static private Set<String> copyFeatureSet(Set<String> o)
//package com.java2s; //License from project: Apache License import java.util.*; public class Main { static private Set<String> copyFeatureSet(Set<String> o) { Set<String> res = new HashSet<>(); for (String s : o) { res.add(s);/*from w w w. ja va2 s. c om*/ } return res; } }