不能用Hashmap一定要用LinkedHashMap因为是有序的 import java.util.LinkedHashMap; import java.util.Map; public class TestGeneral { public static void main(String[] args) { //store orignal User and Country Map hmOriginal = new LinkedHashMap(); hmOriginal.put("John", "Canada"); hmOriginal.put("Bob", "USA"); hmOriginal.put("Tom", "USA"); hmOriginal.put("Alice", "Canada"); hmOriginal.put("Alan", "Canada"); hmOriginal.put("Peter", "UK"); //store Updated data Map hmUpdated = new LinkedHashMap(); for (Map.Entry entry : hmOriginal.entrySet()) { String sName = entry.getKey(); String sCountry = entry.getValue(); if( !hmUpdated.containsValue(sCountry)) { hmUpdated.put(sName, sCountry); } } System.out.println("Original data is :"+hmOriginal ); System.out.println("Updated data is :"+hmUpdated ); } }