随笔-144  评论-80  文章-1  trackbacks-0
java.util

Interface

Collection

RetainAll :保留两个Collection的交集。注意,如果该Collection是由Arrays.asList转换而来,那么这个方法会失败。因为转换来的List接口不支持这个方法

Samples

public static void collectionTest()

    {

        Collection c1 = new ArrayList();

        Collection c2 = new ArrayList();

        c1.add("aaa");

        c1.add("bbb");

        c1.add("ccc");

        c2.add("ddd");

        c2.add("ccc");

        c2.add("eee");

        boolean isRetainSucceed = false;

        isRetainSucceed = c2.retainAll(c1);

        System.out.println("isRetainSucceed = " + isRetainSucceed);

        System.out.println("********** print collection c2 values ");

        for (Iterator iter = c2.iterator(); iter.hasNext();)

        {

            String s = (String) iter.next();

            System.out.println("s = " + s);

        }

}

Enumeration

太简单,参考文档

Comparator

未使用过

EventListener

空接口

Iterator

Enumeration 的不同点:

1. 允许遍历Collection时删除对象

2. 方法名字可读性更好

List

实现的四个类:AbstractList, ArrayList, LinkedList, Vector

List 特点:

1. 允许重复元素,允许null元素

2. 推荐用Iterator遍历,而不是用索引

addAll : 加入Collection

containsAll :是否包含Collection

retainAll : 保留和Collection的交集

subList : 返回指定索引区间的子List

ListIterator

1. 提供元素的双向遍历,而不是单向

2. 遍历时可改变存储的元素

3. 可动态插入元素,插入的元素在当前操作元素的上一个位置

Samples

public static void ListTest(){

        System.out.println("**********ListTest begin:");

        List list = new ArrayList();

        list.add("aaa");

        list.add("bbb");

        list.add("ccc");

        ListIterator iter = list.listIterator();

        System.out.println("**************** Iterating List forward :");

        while(iter.hasNext()){

            String s = (String)iter.next();

            System.out.println("**********element = " + s);

        }

        System.out.println("**************** Iterating List backward :");

        while(iter.hasPrevious()){

            String s = (String)iter.previous();

            System.out.println("**********element = " + s);

        }

        System.out.println("**************** Add element into List :");

        while(iter.hasNext()){

            int i = iter.nextIndex();

            if (i==2)

                iter.add("ddd");

            String s = (String)iter.next();

            System.out.println("**********element = " + s);

        }

        System.out.println("**************** Iterating List backward after add element:");

        while(iter.hasPrevious()){

            String s = (String)iter.previous();

            System.out.println("**********element = " + s);

        }

        System.out.println("**********ListTest end:");

    }

Map

KeySet :

返回Set对象,然后可以遍历这个Set。其中的每个元素都是Map.Entry对象

Map.Entry.setValue :

在遍历Entry对象时,可以改变该Key对应的Value

Samples

public static void mapEntrySetTest(){

        System.out.println("**********mapEntrySetTest begin:");

        Map map = new HashMap();

        map.put("first","aaa");

        map.put("second","bbb");

        map.put("third","ccc");

        map.put("fourth","ddd");

        Set set = map.entrySet();

        Map.Entry entry = null;

        System.out.println("********** print values in map :");

        for(Iterator iter = set.iterator();iter.hasNext();){

            entry = (Map.Entry)iter.next();

            System.out.println("Key is :" + entry.getKey() + " and Value is :" + entry.getValue());

            entry.setValue((String)entry.getValue() + "_setValueTest");

        }

        System.out.println("********** After set value ,iterating values in map :");

        for(Iterator iter = set.iterator();iter.hasNext();){

            entry = (Map.Entry)iter.next();

            System.out.println("Key is :" + entry.getKey() + " and Value is :" + entry.getValue());           

        }

        System.out.println("**********mapEntrySetTest end:");

}

Observable and Observer

暂未想通

RandomAccess

空接口。实现这个接口的List实现品,表示他们支持高速的随机访问元素。如果实现这个接口,理论上

for (int i=0, n=list.size(); i < n; i++)

         list.get(i);

比下面代码要快:

for (Iterator i=list.iterator(); i.hasNext(); )

         i.next();

Set

没什么特别的,和Collection差不多


转自:http://blog.csdn.net/WalkingWithJava/

posted on 2005-04-19 11:25 小力力力 阅读(314) 评论(0)  编辑  收藏 所属分类: JAVA

只有注册用户登录后才能发表评论。


网站导航: