ListOrderedMap和Map

ListOrderedMap位于commons-collections的jar包里，与普通的map相比，ListOrderedMap的key可保持原有顺序。

package util;
 
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
 
import org.apache.commons.collections.map.ListOrderedMap;
 
public class ListOrderMapTest {
 
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<String, String>();  
        map.put("1", "Test1");  
        map.put("2", "Test2");  
        map.put("3", "Test3");  
        map.put("4", "Test4");  
  
        Set<String> set1 = map.keySet();
        for (String key : set1) {
            System.out.println(key + ":" + map.get(key));
        }
        
        System.out.println("---------------------------------------");
  
        @SuppressWarnings("unchecked")
        Map<String, String> listOrderedMap = ListOrderedMap.decorate(new HashMap<String, String>());
        listOrderedMap.put("1", "Test1");  
        listOrderedMap.put("2", "Test2");  
        listOrderedMap.put("3", "Test3");  
        listOrderedMap.put("4", "Test4");  
  
        Set<String> set2 = listOrderedMap.keySet();
        for (String key : set2) {
            System.out.println(key + ":" + listOrderedMap.get(key));
        }

运行结果如下：

3:Test3
2:Test2
1:Test1
4:Test4
---------------------------------------
1:Test1
2:Test2
3:Test3
4:Test4