遍历集合的常见的集中方法

package com.sina.www;
import java.util.*;
publicclass Test3 {
      publicstaticvoid main(String[] args) {
           List l = new ArrayList();
           l.add("世界你好！");
           l.add("上海");
           for (int i = 0; i < l.size(); i++) { // 普通的for循环取出集合中的元素
                 System.out.print(l.get(i));

           }
           System.out.println();
           for (Object o : l) { // 增强for循环取出集合中的元素
                 System.out.print(o);
           }
           System.out.println();
           for (Iterator it = l.iterator(); it.hasNext();) { // 利用迭代器取出集合中的元素

                 System.out.print(it.next());

           }

           System.out.println();
           Iterator it = l.iterator(); //利用迭代器取出集合中的元素
           while (it.hasNext()) {
                 System.out.print(it.next());

           }

      }

}

java中遍历MAP的几种方法

   1. Map<String,String> map=new HashMap<String,String>();
   2. map.put("username", "qq");
   3. map.put("passWord", "123");
   4. map.put("userID", "1");
   5. map.put("email", "qq@qq.com");

Map<String,String> map=new HashMap<String,String>();
map.put("username", "qq");
map.put("passWord", "123");
map.put("userID", "1");
map.put("email", "qq@qq.com");

第一种用for循环
Java代码

   1. for(Map.Entry<String, String> entry:map.entrySet()){
   2.      System.out.println(entry.getKey()+"--->"+entry.getValue());
   3. }

for(Map.Entry<String, String> entry:map.entrySet()){
System.out.println(entry.getKey()+"--->"+entry.getValue());
}

第二种用迭代
Java代码

   1. Set set = map.entrySet();
   2. Iterator i = set.iterator();
   3. while(i.hasNext()){
   4.      Map.Entry<String, String> entry1=(Map.Entry<String, String>)i.next();
   5.      System.out.println(entry1.getKey()+"=="+entry1.getValue());
   6. }

Set set = map.entrySet();
Iterator i = set.iterator();
while(i.hasNext()){
    Map.Entry<String, String> entry1=(Map.Entry<String, String>)i.next();
    System.out.println(entry1.getKey()+"=="+entry1.getValue());
}

用keySet()迭代
Java代码

   1. Iterator it=map.keySet().iterator();
   2. while(it.hasNext()){
   3.      String key;
   4.      String value;
   5.      key=it.next().toString();
   6.      value=map.get(key);
   7.      System.out.println(key+"--"+value);
   8. }

Iterator it=map.keySet().iterator();
while(it.hasNext()){
    String key;
    String value;
    key=it.next().toString();
    value=map.get(key);
    System.out.println(key+"--"+value);
}

用entrySet()迭代
Java代码

   1. Iterator it=map.entrySet().iterator();
   2. System.out.println( map.entrySet().size());
   3. String key;
   4. String value;
   5. while(it.hasNext()){
   6.         Map.Entry entry = (Map.Entry)it.next();
   7.         key=entry.getKey().toString();
   8.         value=entry.getValue().toString();
   9.         System.out.println(key+"===="+value);
10. }

package com.sina.www;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class MapTest2 {
public static void main(String[] args) {
Map<String, String> m = new HashMap<String, String>();
// m.put(001, new Person("关羽", 23));
// m.put(002, new Person("刘备", 24));
// m.put(003, new Person("百度", 22));
//
m.put("sa", "123");
m.put("sb", "143");
m.put("sc", "153");
m.put("sd", "184");
Set keyset = m.keySet(); // 对Map集合的迭代方法一keyset 迭代
Iterator it = keyset.iterator();
while (it.hasNext()) {
   String p = (String) it.next();
   System.out.print("value=" + m.get(p) + " ");
}
// System.out.println(m.get("sa"));
Iterator it2 = m.entrySet().iterator(); // Map集合的迭代方法二entrySet迭代
System.out.println();
System.out.println("长度为" + m.entrySet().size());
String key;
补充：软件开发 , Java ,