Java集合Set、List、Map的遍历方法

具体方法如下：

package com.shellway.javase;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.junit.Test;

public class TestCollection {

  public static void print(Collection extends Object> c){
    Iterator extends Object> it = c.iterator();
    while (it.hasNext()) {
      Object object = (Object) it.next();
      System.out.println(object);
    }
  }

  @Test
  public void demo1(){
    Set set = new HashSet();
    set.add( "AAA" );
    set.add( "BBB" );
    set.add( "CCC" );
    print(set);

    //Set的第一种遍历方式:利用Iterator
    Iterator it1 = set.iterator();
    for (String ss : set) {
      System.out.println(ss);
    }
    //Set的第一种遍历方式:利用foreach
    for (String sss : set) {
      System.out.println(sss);
    }

    List list = new ArrayList();
    list.add( "DDDDD" );
    list.add( "EEEEE" );
    list.add( "FFFFF" );
    print(list);

    //List的第一种遍历方式:因为list有顺序，利用size()和get()方法获取
    for ( int i = 0 ; i < list.size(); i++) {
      System.out.println(list.get(i));
    }
    //List的第二种遍历方式：利用Iterator
    Iterator it = list.iterator();
    while (it.hasNext()) {
      System.out.println(it.next());
    }
    //List的第三种遍历方式:利用foreach
    for (String s2 : list) {
      System.out.println(s2);
    }

    Map map = new TreeMap();
    map.put( "Jerry" , "10000" );
    map.put( "shellway" , "20000" );
    map.put( "Kizi" , "30000" );
    print(map.entrySet());
    //Map的第一种遍历方式：先获得key,再获得值value
    Set sett = map.keySet();
    for (String s : sett) {
      System.out.println(s+ ":" +map.get(s));
    }
    //Map的第二种遍历方式：获得键值对
    for (Map.Entry entry : map.entrySet()) {
      System.out.println(entry.getKey()+ " : " +entry.getValue());
    }
  }
}