ListOrderedMap与Map的区别

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，在某些情况比如做报表的时候，非常实用。 
代码例子如下：

public class TestListOrderedMap {

    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<Entry<String, String>> entrySet1 = map.entrySet();
        for (Entry<String, String> entry : entrySet1) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }

        Map<String, String> listOrderedMap = ListOrderedMap.decorate(new HashMap());
        listOrderedMap.put("1", "Test1");
        listOrderedMap.put("2", "Test2");
        listOrderedMap.put("3", "Test3");
        listOrderedMap.put("4", "Test4");

        Set<Entry<String, String>> entrySet2 = listOrderedMap.entrySet();
        for (Entry<String, String> entry : entrySet2) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
    }
}