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
和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值
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/