通用类 - Java中的初始化

Question

So I have a generic pool that I'm using and I was wondering what is actually happening at initialisation? Is it creating a Teacher and passing it to the Pool to use, if so what costs does this have?

final Pool<Teacher> pool = new Teacher();

Note: Pool is an Abstract Class & Teacher extends Pool Thanks in advance!

Here's the Pool Class:

public abstract class ObjectPool<T> {
private long expirationTime;

private Hashtable<T, Long> locked, unlocked;

public ObjectPool() {
expirationTime = 30000; // 30 seconds
locked = new Hashtable<T, Long>();
unlocked = new Hashtable<T, Long>();
 }

protected abstract T create();

public abstract boolean validate(T o);

public abstract void expire(T o);

public synchronized T checkOut() {
long now = System.currentTimeMillis();
T t;
if (unlocked.size() > 0) {
  Enumeration<T> e = unlocked.keys();
  while (e.hasMoreElements()) {
    t = e.nextElement();
    if ((now - unlocked.get(t)) > expirationTime) {
      // object has expired
      unlocked.remove(t);
      expire(t);
      t = null;
    } else {
      if (validate(t)) {
        unlocked.remove(t);
        locked.put(t, now);
        return (t);
      } else {
        // object failed validation
        unlocked.remove(t);
        expire(t);
        t = null;
      }
    }
  }
}
// no objects available, create a new one
t = create();
locked.put(t, now);
return (t);
}

public synchronized void checkIn(T t) {
locked.remove(t);
unlocked.put(t, System.currentTimeMillis());
}
}

Answer 1

Assuming the Pool is a data structure for storing objects, you probably want to initialize the Pool instead

final Pool<Teacher> pool = new Pool<>();

If you have a pool where teacher has to extend that anyhow, it seems somewhat awkward and unnecessary.

Edit:

Based on your updated question, I would say to separate the the class up a bit into a pool (manager) class, and an interface that pool objects would implement. Then for your generic class:

public class Pool<T extends PoolObject> {//...

And from there, you can work with the generic PoolObjects, and teacher wouldn't directly implement/extend the pool.