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));
}
}
}
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.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());
}
}
}
0
1
2
3
4
-------2-----
0
1
2
3
4
Process finished with exit code 0
HashMap的两种排序方式
Map<String, Integer> map = new HashMap<String, Integer>();
map.put("d", 2);
map.put("c", 1);
map.put("b", 1);
map.put("a", 3); List<Map.Entry<String, Integer>> infoIds =
new ArrayList<Map.Entry<String, Integer>>(map.entrySet()); //排序前
for (int i = 0; i < infoIds.size(); i++) {
String id = infoIds.get(i).toString();
System.out.println(id);
}
//d 2
//c 1
//b 1
//a 3 //排序
Collections.sort(infoIds, new Comparator<Map.Entry<String, Integer>>() {
public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
//return (o2.getValue() - o1.getValue());
return (o1.getKey()).toString().compareTo(o2.getKey());
}
}); //排序后
for (int i = 0; i < infoIds.size(); i++) {
String id = infoIds.get(i).toString();
System.out.println(id);
}
//根据key排序
//a 3
//b 1
//c 1
//d 2
//根据value排序
//a 3
//d 2
//b 1
//c 1
/**
* 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());
// }
}
}
1
2
3
4
------1-----
4
3
2
1
0
------2-----
Process finished with exit code 0
1 经典的for循环
- public static void main(String[] args) {
- List<String> list = new ArrayList();
- list.add("123");
- list.add("java");
- list.add("j2ee");
- System.out.println("=========经典的for循环=======");
- for(int i=0; i<list.size();i++){
- System.out.println(list.get(i));
- }
- }
2 增强的for循环
- public static void main(String[] args) {
- List<String> list = new ArrayList();
- list.add("123");
- list.add("java");
- list.add("j2ee");
- System.out.println("=========Java1.6的for循环=======");
- for(String s:list){
- System.out.println(s);
- }
- }
3 Iterate的使用
- public static void main(String[] args) {
- List<String> list = new ArrayList();
- list.add("123");
- list.add("java");
- list.add("j2ee");
- System.out.println("=========Iterate循环=======");
- Iterator<String> iter = list.iterator();
- while(iter.hasNext()){
- System.out.println(iter.next());
- }
- }