java 以枚举为键的 HashMap
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HashMap for enum as key
提问by vidhya
I had posted somewhat similar question before also. I got clarification for my doubts as well. But still I need something more. The Hashmap will be initialized with the enum object as the key and a threadpool instance as the value. I am confused as of how to initialize the HashMap for every object been called by some other process ..To make clear :
My program, MyThreadpoolExcecutorPgm.java initializes a HashMap
My Progran AdditionHandler.java requests a thread from the HashMap by passing ThreadpoolName (enum). I am getting "No thread available from HashMap" message. Please do help me.
Below given is my code:
我之前也发布过类似的问题。我的疑惑也得到了澄清。但我仍然需要更多的东西。Hashmap 将使用枚举对象作为键和线程池实例作为值进行初始化。我对如何为其他进程调用的每个对象初始化 HashMap 感到困惑。 ）。我收到“HashMap 中没有可用线程”消息。请帮助我。
下面给出的是我的代码：
public class MyThreadpoolExcecutorPgm {
enum ThreadpoolName {
DR, BR, SV, MISCELLENEOUS;
}
private static String threadName;
private static HashMap<ThreadpoolName, ThreadPoolExecutor>
threadpoolExecutorHash;
public MyThreadpoolExcecutorPgm(String p_threadName) {
threadName = p_threadName;
}
public static void fillthreadpoolExecutorHash() {
int poolsize = 3;
int maxpoolsize = 3;
long keepAliveTime = 10;
ThreadPoolExecutor tp = null;
threadpoolExecutorHash = new HashMap<ThreadpoolName, ThreadPoolExecutor>();
for (ThreadpoolName poolName : ThreadpoolName.) // failing to implement
{
tp = new ThreadPoolExecutor(poolsize, maxpoolsize, keepAliveTime,
TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(5));
threadpoolExecutorHash.put(poolName, tp);
}
}
public static ThreadPoolExecutor getThreadpoolExcecutor(
ThreadpoolName poolName) {
ThreadPoolExecutor thread = null;
if (threadpoolExecutorHash != null && poolName != null) {
thread = threadpoolExecutorHash.get(poolName);
} else {
System.out.println("No thread available from HashMap");
}
return thread;
}
}
AdditionHandler.java
加法处理程序
public class AdditionHandler{
public void handle() {
AddProcess setObj = new AddProcess(5, 20);
ThreadPoolExecutor tpe = null;
ThreadpoolName poolName =ThreadpoolName.DR; //i am using my enum
tpe = MyThreadpoolExcecutorPgm.getThreadpoolExcecutor(poolName);
tpe.execute(setObj);
}
public static void main(String[] args) {
AdditionHandler obj = new AdditionHandler();
obj.handle();
}
}
回答by Jon Skeet
I suspect you're just looking for the static values()method which is added to every enum:
我怀疑您只是在寻找values()添加到每个枚举中的静态方法：
for (ThreadpoolName poolName : ThreadpoolName.getValues())
Alternatively, you can use EnumSet.allOf():
或者，您可以使用EnumSet.allOf()：
for (ThreadpoolName poolName : EnumSet.allOf(ThreadpoolName.class))
(As Bozho says, EnumMapis a good alternative here. You still need to loop through the enum values.)
（正如 Bozho 所说，EnumMap这里是一个不错的选择。您仍然需要遍历枚举值。）
回答by Bozho
回答by OrangeDog
You can iterate through enum values by one of (in descending order of preference)
您可以通过其中之一（按偏好的降序）遍历枚举值
for(Enum value : Enum.values())
for(Enum value : EnumSet.allOf(Enum.class))
for(Enum value : Enum.class.getEnumConstants())
But you should also be using an EnumMap.
但是您也应该使用EnumMap.
