Java集合的Stack、Queue、Map的遍历

import java.util.HashMap; 
import java.util.Iterator; 
import java.util.Map; 

/** 
* Map的遍历，这个遍历比较特殊，有技巧 
* 
* @author leizhimin 2009-7-22 15:15:34 
*/ 
public  class TestMap { 
         public  static  void main(String[] args) { 
                Map<String, String> map =  new HashMap<String, String>(); 
                map.put( "1",  "a"); 
                map.put( "2",  "b"); 
                map.put( "3",  "c"); 

                 //最简洁、最通用的遍历方式 
                 for (Map.Entry<String, String> entry : map.entrySet()) { 
                        System.out.println(entry.getKey() +  " = " + entry.getValue()); 
                } 
                 //Java5之前的比较简洁的便利方式1 
                System.out.println( "----1----"); 
                 for (Iterator<Map.Entry<String, String>> it = map.entrySet().iterator(); it.hasNext();) { 
                        Map.Entry<String, String> entry = it.next(); 
                        System.out.println(entry.getKey() +  " = " + entry.getValue()); 
                } 
                 //Java5之前的比较简洁的便利方式2 
                System.out.println( "----2----"); 
                 for (Iterator<String> it = map.keySet().iterator(); it.hasNext();) { 
                        String key = it.next(); 
                        System.out.println(key +  " = " + map.get(key)); 
                } 
        } 
}

3 = c 
2 = b 
1 = a 
----1---- 
3 = c 
2 = b 
1 = a 
----2---- 
3 = c 
2 = b 
1 = a 

Process finished with exit code 0

import java.util.Queue; 
import java.util.concurrent.LinkedBlockingQueue; 

/** 
* 队列的遍历 
* 
* @author leizhimin 2009-7-22 15:05:14 
*/ 
public  class TestQueue { 
         public  static  void main(String[] args) { 
                Queue<Integer> q =  new LinkedBlockingQueue<Integer>(); 
                 //初始化队列 
                 for ( int i = 0; i < 5; i++) { 
                        q.offer(i); 
                } 
                System.out.println( "-------1-----"); 
                 //集合方式遍历，元素不会被移除 
                 for (Integer x : q) { 
                        System.out.println(x); 
                } 
                System.out.println( "-------2-----"); 
                 //队列方式遍历，元素逐个被移除 
                 while (q.peek() !=  null) { 
                        System.out.println(q.poll()); 
                } 
        } 
}

-------1----- 
0 
1 
2 
3 
4 
-------2----- 
0 
1 
2 
3 
4 

Process finished with exit code 0

import java.util.Stack; 

/** 
* 栈的遍历 
* 
* @author leizhimin 2009-7-22 14:55:20 
*/ 
public  class TestStack { 
         public  static  void main(String[] args) { 
                Stack<Integer> s =  new Stack<Integer>(); 
                 for ( int i = 0; i < 10; i++) { 
                        s.push(i); 
                } 
                 //集合遍历方式 
                 for (Integer x : s) { 
                        System.out.println(x); 
                } 
                System.out.println( "------1-----"); 
                 //栈弹出遍历方式 
//                while (s.peek()!=null) {     //不健壮的判断方式，容易抛异常，正确写法是下面的 
                 while (!s.empty()) { 
                        System.out.println(s.pop()); 
                } 
                System.out.println( "------2-----"); 
                 //错误的遍历方式 
//                for (Integer x : s) { 
//                        System.out.println(s.pop()); 
//                } 
        } 
}

0 
1 
2 
3 
4 
------1----- 
4 
3 
2 
1 
0 
------2----- 

Process finished with exit code 0