Java Map的几种循环方式学习总结

Map<Object , Object> map = new HashMap<Object, Object>();
for (int i = 0; i < 10; i++) {
map.put(i, i+1);
}
for (Object key : map.keySet()) {
System.out.println("key = " + key);
}

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

Iterator it = paraMap.entrySet().iterator();
while (it.hasNext())
{
Map.Entry map = (Map.Entry)it.next();
System.out.println(map .getKey() + " = " + map .getValue());
}

package com.dufyun.javase.jihe;

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

/**
* 练习循环map集合中key和value的方法
* @author aflyun
*
*
*/
public class TestMap {

public static void main(String[] args) {
Map<Object , Object> map = new HashMap<Object, Object>();
for (int i = 0; i < 10; i++) {
map.put(i, i+1);
}

firstLoopMap(map);
secodnLoopMap(map);
thirdLoopMap(map);
}

/**
* 1：循环 map 中的key<br/>
* 	 根据JDK的新特性,用For循环Map,例如循环Map的Key 和 value
* @param map
*/
public static void firstLoopMap(Map<Object, Object> map) {
for (Object key : map.keySet()) {
System.out.println("key = " + key +"--value = " + map.get(key));
}
}
/**
* 2：循环 map 中的key 和 value<br/>
* entrySet
* @param map
*/
public static void secodnLoopMap(Map<Object , Object> map) {
for (Map.Entry<Object, Object> entry : map.entrySet()) {
System.out.println("key = " + entry.getKey() +"--value = " + entry.getValue());
}
}

/**
* 3:循环Map的key 和value<br/>
* iterator
* @param map
*/
public static void thirdLoopMap(Map<Object, Object> map) {
Iterator it = map.entrySet().iterator();
while(it.hasNext()){
Map.Entry<Object, Object> m = (Entry<Object, Object>) it.next();
System.out.println("key = " + m.getKey() +"---value = "+ m.getValue());
}

}
}

key = 0---value = 1
key = 1---value = 2
key = 2---value = 3
key = 3---value = 4
key = 4---value = 5
key = 5---value = 6
key = 6---value = 7
key = 7---value = 8
key = 8---value = 9
key = 9---value = 10