Java中遍历ConcurrentHashMap的四种方式详解

System.out.println("方式一：在for-each循环中使用entries来遍历");
for (Map.Entry<String, String> entry: map.entrySet()) {
 System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

System.out.println("方法二：在for-each循环中遍历keys或values,这种方式适用于需要值或者键的情况");
//遍历键
for (String key : map.keySet()) {
 System.out.println("key = " + key);
}
//遍历值
for (String value : map.values()) {
 System.out.println("value = " + value);
}

//使用泛型
Iterator<Map.Entry<String, String>> entries = map.entrySet().iterator();
System.out.println("使用Iterator遍历,并且使用泛型:");
while (entries.hasNext()) {
	Map.Entry<String, String> entry = entries.next();
	System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
	//注意这里操作了集合,下面的的遍历不会再打印0
	if("0".equals(entry.getKey())) {
		map.remove(entry.getKey());
	}
}
//不使用泛型
Iterator entrys = map.entrySet().iterator();
System.out.println("使用Iterator遍历,并且不使用泛型");
while (entrys.hasNext()) {
	Map.Entry entry = (Map.Entry) entrys.next();
	String key = (String)entry.getKey();
	String value = (String)entry.getValue();
	System.out.println("Key = " + key + ", Value = " + value);
}

System.out.println("方式四：通过键找值遍历");
for (String key : map.keySet()) {
	String value = map.get(key);
	System.out.println("Key = " + key + ", Value = " + value);
}
}