常见Map 及 ArrayList 是否有序总结

说明：此处的排序 是指：

1： 往集合中插入元素的顺序与遍历元素的顺序的关系；

2： 往对象中插入元素否会根据元素的大小排序

 

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public class MapSortTest {         public static void main(String[] args) {                     System.out.println( "放入顺序为：a:aaa c:ccc b:bbb d:ddd " );          System.out.println( "HashMap 排序测试" );          Map map = new HashMap();           map.put( "a" , "aaa" );            map.put( "c" , "ccc" );          map.put( "b" , "bbb" );           map.put( "d" , "ddd" );           Iterator iterator = map.keySet().iterator();           while (iterator.hasNext()) {               Object key = iterator.next();               System.out.println( "key:" +key+ "         value:" + map.get(key));           }           System.out.println( "HashMap 进出无次序 ； key大小无次序 " );          System.out.println( "***********************************************************" );                                System.out.println( "Hashtable 排序测试" );                 Hashtable tab = new Hashtable();           tab.put( "a" , "aaa" );           tab.put( "c" , "ccc" );          tab.put( "b" , "bbb" );            tab.put( "d" , "ddd" );           Iterator iterator_1 = tab.keySet().iterator();           while (iterator_1.hasNext()) {               Object key = iterator_1.next();               System.out.println( "key :" +key+ "             value:" + tab.get(key));           }           System.out.println( "Hashtable 进出无次序 ； key大小无次序 " );          System.out.println( "***********************************************************" );                     System.out.println( "TreeMap 排序测试" );                       TreeMap tmp = new TreeMap();           tmp.put( "a" , "aaa" );           tmp.put( "c" , "ccc" );           tmp.put( "b" , "bbb" );           tmp.put( "d" , "ddd" );           Iterator iterator_2 = tmp.keySet().iterator();           while (iterator_2.hasNext()) {               Object key = iterator_2.next();               System.out.println( "key:" +key+ "          value:" + tmp.get(key));           }           System.out.println( "TreeMap 进出无次序 ； key大小从小到大 " );          System.out.println( "***********************************************************" );                     System.out.println( "LinkedHashMap 排序测试" );                         LinkedHashMap linkedHashMap = new LinkedHashMap();           linkedHashMap.put( "a" , "aaa" );           linkedHashMap.put( "c" , "ccc" );           linkedHashMap.put( "b" , "bbb" );           linkedHashMap.put( "d" , "ddd" );           Iterator iterator2 = linkedHashMap.keySet().iterator();           while (iterator2.hasNext()) {               Object key = iterator2.next();               System.out.println( "key:" +key+ "          value:" + linkedHashMap.get(key));           }                 System.out.println( "LinkedHashMap 先进先出； key大小无次序 " );          System.out.println();                     System.out.println( "ArrayList 排序测试" );          System.out.println( "放入顺序为：aaa ccc bbb ddd" );          ArrayList arrayList= new ArrayList();           arrayList.add( "aaa" );           arrayList.add( "ccc" );           arrayList.add( "bbb" );           arrayList.add( "ddd" );           System.out.println( "ArrayList 先进先出；值大小无次序 " ); //      Collections.sort(arrayList);           for ( int i= 0 ;i<arrayList.size();i++){               System.out.println(arrayList.get(i));           }           System.out.println( "***********************************************************" );      }    }

 

运行结果：

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放入顺序为：a:aaa c:ccc b:bbb d:ddd  HashMap 排序测试 key:d         value:ddd key:b         value:bbb key:c         value:ccc key:a         value:aaa HashMap 进出无次序 ； key大小无次序  *********************************************************** Hashtable 排序测试 key :b             value:bbb key :a             value:aaa key :d             value:ddd key :c             value:ccc Hashtable 进出无次序 ； key大小无次序  *********************************************************** TreeMap 排序测试 key:a          value:aaa key:b          value:bbb key:c          value:ccc key:d          value:ddd TreeMap 进出无次序 ； key大小从小到大  *********************************************************** LinkedHashMap 排序测试 key:a          value:aaa key:c          value:ccc key:b          value:bbb key:d          value:ddd LinkedHashMap 先进先出； key大小无次序     ArrayList 排序测试 放入顺序为：aaa ccc bbb ddd LinkedHashMap 先进先出；值大小无次序  aaa ccc bbb ddd ***********************************************************