Java 使用for和while循环遍历HashMap的方法及示例代码

1､使用entrySet()遍历

相关文档：entrySet()

1) 使用while实现

public static void printMap(Map mp) {
    Iterator it = mp.entrySet().iterator();
    while (it.hasNext()) {
        Map.Entry pair = (Map.Entry)it.next();
        System.out.println(pair.getKey() + " = " + pair.getValue());
        it.remove(); // avoids a ConcurrentModificationException
    }
}

2) 使用for实现

for (Map.Entry entry : map.entrySet()) {
    String key = entry.getKey();
    Object value = entry.getValue();
    // ...
}

2､使用for和keySet()或values()实现

相关文档：

values()

keySet()

1) 使用keySet()遍历key

Collection keys = map.keySet();
for(Object key: keys){
    System.out.println("Key " + key);
    System.out.println("Value " + map.get(key));
}

2)使用values()遍历值

Map map = new HashMap();
for (Integer value : map.values()) {
    System.out.println("Value = " + value);
}

3､HashMap使用示例代码

import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map.Entry;public class HashMapTest {public static void main(String[] args) {HashMap map = new HashMap<>();map.put("java", "31");//存放键值对System.out.println(map.containsKey("java"));//键中是否包含这个数据System.out.println(map.containsKey("python"));System.out.println("=========================");System.out.println(map.get("java"));//通过键拿值System.out.println(map.get("python"));System.out.println("=========================");System.out.println(map.isEmpty());//判空System.out.println(map.size());System.out.println("=========================");System.out.println(map.remove("java"));//从键值中删除System.out.println(map.containsKey("python"));System.out.println(map.get("javapy"));//获取值System.out.println(map.isEmpty());System.out.println(map.size());System.out.println("=========================");map.put("wonhero", "31");System.out.println(map.get("wonhero"));map.put("wonhero", "32");System.out.println(map.get("wonhero"));System.out.println("=========================");map.put("wonhero", "1");map.put("javapy", "2");map.put("python", "3");for (String key : map.keySet()) {System.out.println(key);}System.out.println("=========================");for (String values : map.values()) {System.out.println(values);}System.out.println("=========================");map.clear();map.put("A", "1");map.put("B", "2");map.put("C", "3");map.put("D", "1");map.put("E", "2");map.put("F", "3");map.put("G", "1");map.put("H", "2");map.put("I", "3");for (Entry entry : map.entrySet()) {String key = entry.getKey();String value = entry.getValue();System.out.println(key + "," + value);}System.out.println("=========================");List removeKeys = new ArrayList();for (Entry entry : map.entrySet()) {if (!entry.getValue().equals("1")) {removeKeys.add(entry.getKey());}}for (String removeKey : removeKeys) {map.remove(removeKey);}for (Entry entry : map.entrySet()) {String key = entry.getKey();String value = entry.getValue();System.out.println(key + "," + value);}System.out.println("=========================");}}

相关文档：

Java使用hashmap中的数据初始化hashmap并执行put数据的简洁代码

Java hashmap computeIfAbsent()使用方法及示例代码

Java中 static final修饰hashmap静态成员变量初始化方法