praktikum-holons/src/holeg/utility/pooling/Pool.java

package holeg.utility.pooling;

import java.util.ArrayList;
import java.util.stream.Stream;


public abstract class Pool<T> {

  int borrowedCount = 0;
  private int poolCapacity = 1000;
  private final ArrayList<T> poolList = new ArrayList<>(poolCapacity);
  private final ArrayList<T> borrowedList = new ArrayList<>(poolCapacity);


  public Pool() {
    poppulatePool(poolCapacity);
  }

  public abstract T create();

  public T get() {
    checkCapacity(borrowedCount);
    T poolObject = poolList.get(borrowedCount);
    borrowedCount++;
    borrowedList.add(poolObject);
    return poolObject;
  }

  public void clear() {
    borrowedList.clear();
    borrowedCount = 0;
  }


  private void poppulatePool(int amount) {
    for (int i = 0; i < amount; i++) {
      poolList.add(create());
    }
  }

  private void checkCapacity(int requestedCapacity) {
    if (poolCapacity <= requestedCapacity) {
      int newSize = 2 * requestedCapacity;
      poppulatePool(newSize - poolCapacity);
      poolCapacity = 2 * requestedCapacity;
    }
  }

  public int getBorrowedCount() {
    return borrowedCount;
  }

  public Stream<T> getBorrowedStream() {
    return borrowedList.stream();
  }

}