В Java есть 3 способа выполнить цикл или итерацию хэш-карты
1. Если возможно, всегда используйте Java 8 forEach
.
Mapmap = new HashMap<>(); map.forEach((key, value) -> System.out.println("[Key] : " + key + " [Value] : " + value));
2. Нормально для цикла в entrySet()
Mapmap = new HashMap<>(); for (Map.Entry entry : map.entrySet()) { System.out.println("[Key] : " + entry.getKey() + " [Value] : " + entry.getValue()); }
3. Итератор, классический.
Mapmap = new HashMap<>(); Iterator iter = map.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); System.out.println("[Key] : " + entry.getKey() + " [Value] : " + entry.getValue()); }
Пример хэш-карты
Полный пример, просто для справки.
package com.mkyong.calculator; import java.util.HashMap; import java.util.Iterator; import java.util.Map; public class HashMapExample { public static void main(String[] args) { Mapmap = new HashMap<>(); map.put("web", 1024); map.put("database", 2048); map.put("static", 5120); System.out.println("Java 8 forEach loop"); map.forEach((key, value) -> System.out.println("[Key] : " + key + " [Value] : " + value)); System.out.println("for entrySet()"); for (Map.Entry entry : map.entrySet()) { System.out.println("[Key] : " + entry.getKey() + " [Value] : " + entry.getValue()); } System.out.println("Iterator"); Iterator iter = map.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); System.out.println("[Key] : " + entry.getKey() + " [Value] : " + entry.getValue()); } } }
Выход
Java 8 forEach loop [Key] : database [Value] : 2048 [Key] : static [Value] : 5120 [Key] : web [Value] : 1024 for entrySet() [Key] : database [Value] : 2048 [Key] : static [Value] : 5120 [Key] : web [Value] : 1024 Iterator [Key] : database [Value] : 2048 [Key] : static [Value] : 5120 [Key] : web [Value] : 1024
Рекомендации
Оригинал: “https://mkyong.com/java/java-how-to-iterate-a-hashmap/”