遍历map中的元素的几种方法

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

/**
* 遍历map的几种方法
* @author tpf
*
*/
public class TestMapLookup {

public static void main(String[] args) {
Map <String,Integer> map = new HashMap<String,Integer>();
map.put("aaa", 1);
map.put("ccc", 2);
map.put("bbb", 3);

//方法一for
for(Map.Entry<String,Integer> entry: map.entrySet()){
System.out.println(entry.getKey() + "--->" + entry.getValue());
}

//方法二keySet()
Set<String> set = map.keySet();
Iterator <String> it = set.iterator();
while(it.hasNext()) {
String key = it.next();
int value = map.get(key);
System.out.println(key + "--->" + value);
}

//方法三entrySet()
Set<Map.Entry<String, Integer>> set1 = map.entrySet();
Iterator <Map.Entry<String, Integer>> it1 = set1.iterator();
while(it1.hasNext()) {
Map.Entry<String, Integer> entry = it1.next();
System.out.println(entry.getKey() + "---->" + entry.getValue());
}
}
}