查找list中的重复数据，并得到重复数据索引位置

package cn.com.newglobe.action.attendance;import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;public class Test2 {public static void main(String[] args) {List<String> strLs = new ArrayList<String>();strLs.add("1_4");strLs.add("1_7");strLs.add("1_7");strLs.add("1_9");strLs.add("1_9");strLs.add("7_7");strLs.add("9_9");strLs.add("1_13");same(strLs);}public static void same(List<String> list) {Map<String, String> map = new HashMap<String, String>();for (int i = 0; i < list.size(); i++) {String key = list.get(i);String old = map.get(key);if (old != null) {map.put(key, old + "," + (i + 1));} else {map.put(key, "" + (i + 1));}}Iterator<String> it = map.keySet().iterator();while (it.hasNext()) {String key = it.next();String value = map.get(key);if (value.indexOf(",") != -1) {System.out.println(key + " 重复,行： " + value);}}}}