JDK8以下
foreach遍历方式【推荐写法】
public class MapDemo { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "heyi"); map.put(2, "heyi2"); map.put(3, "heyi2"); forMap(map); } //使用增强for + entrySet 进行循环 private static void forMap(Map<Integer, String> map) { for (Map.Entry<Integer, String> entry : map.entrySet()) { System.out.println("key >>>>" + entry.getKey()); System.out.println("Value >>>>>" + entry.getValue()); } } }
Iterator+entrySet写法
Map.Entry是Map接口的内部接口，获取迭代器后使用while依次取出每个迭代器里面的Map.Entry
public class MapDemo { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "heyi"); map.put(2, "heyi2"); map.put(3, "heyi2"); whileIterator(map); } //while+迭代器 private static void whileIterator(Map<Integer, String> map) { //获取迭代器 Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator(); //是否存在下一个 while (iterator.hasNext()) { //获取到下一个 Map.Entry<Integer, String> next = iterator.next(); //输出key System.out.println("Key >>> " + next.getKey()); //输出value System.out.println("Value >>>>>" + next.getValue()); } } }
Iterator+keyset写法
不推荐，只能获取key，然后通过key获取对应的value,重复计算
public class MapDemo { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "heyi"); map.put(2, "heyi2"); map.put(3, "heyi2"); whileKey(map); } //while+迭代器获取key private static void whileKey(Map<Integer, String> map) { Iterator<Integer> iterator = map.keySet().iterator(); while (iterator.hasNext()) { Integer key = iterator.next(); String value = map.get(key); System.out.println("Key >>>> " + key); System.out.println("Value >>>>>" + value); } } }
JDK8
foreach lambda遍历方式【推荐写法 简捷】
public class MapDemo { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "heyi"); map.put(2, "heyi2"); map.put(3, "heyi2"); foreachMap(map); } private static void foreachMap(Map<Integer, String> map) { map.forEach((key, value) -> { System.out.println("key >>> " + key); System.out.println("value >>>>> " + value); }); } }
stream流遍历Map【不推荐写法，重复计算】
如果Map集合存在一些中间处理，可以过滤操作，使用流式遍历也很方便。
public class MapDemo { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "heyi"); map.put(2, "heyi2"); map.put(3, "heyi2"); streamForeach(map); } private static void streamForeach(Map<Integer, String> map) { map.entrySet().stream().forEach((Map.Entry<Integer, String> enTry) -> { System.out.println("key >>> " + enTry.getKey()); System.out.println("value >>>>> " + enTry.getValue()); }); } }
