如何使用抽象类将内存分配给实例数组？

public abstract class MemoryAllocator {
    protected int size;

    public MemoryAllocator(int size) {
        this.size = size;
    }

    public abstract void allocateMemory();

    public abstract void freeMemory();

    public int getSize() {
        return size;
    }
}

public class ArrayMemoryAllocator extends MemoryAllocator {
    private int[] memory;

    public ArrayMemoryAllocator(int size) {
        super(size);
    }

    public void allocateMemory() {
        memory = new int[getSize()];
    }

    public void freeMemory() {
        memory = null;
    }
}

public class Main {
    public static void main(String[] args) {
        MemoryAllocator[] allocators = new MemoryAllocator[3];

        allocators[0] = new ArrayMemoryAllocator(1024);
        allocators[1] = new ArrayMemoryAllocator(2048);
        allocators[2] = new ArrayMemoryAllocator(4096);

        for (MemoryAllocator allocator : allocators) {
            allocator.allocateMemory();
            System.out.println("Allocated memory of size: " + allocator.getSize());
        }

        for (MemoryAllocator allocator : allocators) {
            allocator.freeMemory();
        }
    }
}