Java 高性能遍历 Map 的三种方式

常规遍历，能满足大部分场景

Map<Integer, Integer> map = new HashMap<Integer, Integer>();

for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
 }

按需遍历，更高性能

Map<Integer, Integer> map = new HashMap<Integer, Integer>();

//遍历map中的键
for (Integer key : map.keySet()) {
    System.out.println("Key = " + key);
}

//遍历map中的值
for (Integer value : map.values()) {
    System.out.println("Value = " + value);
}

Iterator 遍历，过程可删除元素

Map<Integer, Integer> map = new HashMap<Integer, Integer>();
Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();

while (entries.hasNext()) {
    Map.Entry<Integer, Integer> entry = entries.next();
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
    entries.remove();
}