遍历map集合

最新推荐文章于 2022-01-27 00:08:32 发布

转载最新推荐文章于 2022-01-27 00:08:32 发布 · 452 阅读

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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);
    }
   }
}
}