java遍历map的五种方法

package com.jackey.topic;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Set;

//循环遍历map的方法

public class CircleMap {

 public static void main(String[] args) {

  Map<String, Integer> tempMap = new HashMap<String, Integer>();

  tempMap.put("a", 1);

  tempMap.put("b", 2);

  tempMap.put("c", 3);

  // JDK1.4中

  // 遍历方法一 hashmap entrySet() 遍历

  System.out.println("方法一");

  Iterator it = tempMap.entrySet().iterator();

  while (it.hasNext()) {

   Map.Entry entry = (Map.Entry) it.next();

   Object key = entry.getKey();

   Object value = entry.getValue();

   System.out.println("key=" + key + " value=" + value);

  }

  System.out.println("");

  // JDK1.5中,应用新特性For-Each循环
  // 遍历方法二

  System.out.println("方法二");

  for (Map.Entry<String, Integer> entry : tempMap.entrySet()) {

   String key = entry.getKey().toString();

   String value = entry.getValue().toString();

   System.out.println("key=" + key + " value=" + value);

  }

  System.out.println("");

  // 遍历方法三 hashmap keySet() 遍历

  System.out.println("方法三");

  for (Iterator i = tempMap.keySet().iterator(); i.hasNext();) {

   Object obj = i.next();

   System.out.println(obj);// 循环输出key

   System.out.println("key=" + obj + " value=" + tempMap.get(obj));

  }
  for (Iterator i = tempMap.values().iterator(); i.hasNext();) {

   Object obj = i.next();

   System.out.println(obj);// 循环输出value

  }

  System.out.println("");

  // 遍历方法四 treemap keySet()遍历
  System.out.println("方法四");

  for (Object o : tempMap.keySet()) {

   System.out.println("key=" + o + " value=" + tempMap.get(o));

  }

  System.out.println("11111");

  // java如何遍历Map <String, ArrayList> map = new HashMap <String,

  // ArrayList>();

  System.out
    .println("java  遍历Map <String, ArrayList> map = new HashMap

<String, ArrayList>();");

  Map<String, ArrayList> map = new HashMap<String, ArrayList>();

  Set<String> keys = map.keySet();

  Iterator<String> iterator = keys.iterator();

  while (iterator.hasNext()) {

   String key = iterator.next();

   ArrayList arrayList = map.get(key);

   for (Object o : arrayList) {

    System.out.println(o + "遍历过程");

   }

  }

  System.out.println("2222");
  Map<String, List> mapList = new HashMap<String, List>();

  for (Map.Entry entry : mapList.entrySet()) {

   String key = entry.getKey().toString();

   List<String> values = (List) entry.getValue();

   for (String value : values) {

    System.out.println(key + " --> " + value);

   }

  }

 }

}