java 遍历map 方法 集合 五种的方法

以下是转载别人的日志，以方便自己以后使用，仅供自己学习之用。

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); } } } }