常见Map 及 ArrayList 是否有序总结

来源：互联网发布：jonas kaufmann 知乎编辑：程序博客网时间：2024/05/05 17:34
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
public class MapSortTest {     publicstatic 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=newArrayList();        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(inti=0;i<arrayList.size();i++){            System.out.println(arrayList.get(i));        }        System.out.println("***********************************************************");    } }
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