list、set、map的遍历方式

https://blog.csdn.net/sunrainamazing/article/details/71577662

list的四种遍历方式，遍历list集合

list 遍历元素 
http://blog.csdn.net/sunrainamazing/article/details/71577662

set遍历元素 
http://blog.csdn.net/sunrainamazing/article/details/71577893

map遍历元素 
http://blog.csdn.net/sunrainamazing/article/details/71580051

package sun.rain.amazing.traversal;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

/**
 * Created by sunRainAmazing on SUN_RAIN_AMAZING
 * @author sunRainAmazing
 */
public class TraversalList {
    //http://www.cnblogs.com/interdrp/p/3663602.html
    public static void main(String args[]){

        List<String> list = new ArrayList<String>(
            Arrays.asList("tom","cat","Jane","jerry"));



        //方法1 集合类的通用遍历方式, 从很早的版本就有, 用迭代器迭代
        Iterator it1 = list.iterator();
        while(it1.hasNext()){
            System.out.println(it1.next());
        }



        //方法2 集合类的通用遍历方式, 从很早的版本就有, 用迭代器迭代
        for(Iterator it2 = list.iterator();it2.hasNext();){
            System.out.println(it2.next());
        }



        //方法3 增强型for循环遍历
        for(String value:list){
            System.out.println(value);
        }



        //方法4 一般型for循环遍历
        for(int i = 0;i < list.size(); i ++){
            System.out.println(list.get(i));
        }



    }


}

package sun.rain.amazing.traversal;

import java.util.*;

/**
 * Created by sunRainAmazing on SUN_RAIN_AMAZING
 * @author sunRainAmazing
 */
public class TraversalSet {
    public static void main(String args[]){

        List<String> list = new ArrayList<>(
            Arrays.asList("tom","cat","Jane","jerry"));
        Set<String> set = new HashSet<>();
        set.addAll(list);



        //方法1 集合类的通用遍历方式, 从很早的版本就有, 用迭代器迭代
        Iterator it1 = set.iterator();
        while(it1.hasNext()){
            System.out.println(it1.next());
        }



        //方法2 集合类的通用遍历方式, 从很早的版本就有, 用迭代器迭代
        for(Iterator it2 = set.iterator();it2.hasNext();){
            System.out.println(it2.next());
        }



        //方法3 增强型for循环遍历
        for(String value: set){
            System.out.println(value);
        }


    }

}

package sun.rain.amazing.traversal;

import java.util.*;
import java.util.Map.Entry;

/**
 * Created by sunRainAmazing on SUN_RAIN_AMAZING
 * @author sunRainAmazing
 */
public class TraversalMap {

   //http://www.cnblogs.com/toSeeMyDream/p/5577601.html
    public static void main(String[] args){

        Map<String,Integer> map = new HashMap<String,Integer>();
        map.put("tom1",1);
        map.put("tom2",2);
        map.put("tom3",3);
        map.put("tom5",5);
        map.put("tom4",4);

        //1.4版本之前

        Iterator it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            Object key = entry.getKey();
            Object value = entry.getValue();
            System.out.print(key+" -->: "+value+"\t");
        }

        System.out.println("\n================");
        //1.5 for-each 循环操作
        for(String o : map.keySet()){
            System.out.print (map.get(o)+"\t");
        }



        //方法一: 用entrySet()  
        //返回的 set 中的每个元素都是一个 Map.Entry 类型。
        // 推荐，尤其是容量大时
        System.out.println("\n=====用entrySet()=======");
        Iterator it1 = map.entrySet().iterator();
        while(it1.hasNext()){
            Map.Entry m=(Map.Entry)it1.next();
            System.out.println("[name = " + m.getKey() 
                + "] age = " + m.getValue());
        }



        // 方法二：jdk1.5支持，用entrySet()和For-Each循环()
        System.out.println("\n=用entrySet()和For-Each===");
        for (Map.Entry<String, Integer> m : map.entrySet()) {
            System.out.println("[name = " + m.getKey() + "] age = " + m.getValue());
        }




        // 方法三：用keySet() 普遍使用，二次取值
        System.out.println("\n=====用keySet()=======");
        Iterator it2 = map.keySet().iterator();
        while (it2.hasNext()){
            String key = (String) it2.next();
            System.out.println("[name = " + key 
                + "] age = " + map.get(key) );
        }




        // 方法四：jdk1.5支持，用keySEt()和For-Each循环
        System.out.println("\n=====用keySet()和For-Each=====");
        for(Object key: map.keySet()){
            System.out.println("[name = " + key 
                + "] age = " + map.get(key) );
        }


    }





    /**
     * entrySet()
     * @param map
     */
    private void printMap(Map<String,Integer> map){
        Set<Entry<String, Integer>> entries = map.entrySet( );
        if(entries != null) {
            Iterator  iterator = entries.iterator( );
            while(iterator.hasNext( )) {
                Map.Entry  entry =
                    (Entry<String, Integer>) iterator.next( );
//              Object key = entry.getKey();
//              Object value = entry.getValue();

                System.out.println(                       
                    entry.getKey()+"\t\t:"+entry.getValue());
            }
        }

    }



}