java - 堆栈返回对象而不是整数

Question

我正在尝试实现一个涉及堆栈数组的程序。每个堆栈都接受 Integer 对象，但问题是当我尝试从堆栈中获取 Integer 对象时:

import java.util.*;

public class Blocks
{
    public static void main(String[] args)
    {
        System.out.println();
        Scanner input = new Scanner(System.in);

        Stack[] blocks = new Stack[input.nextInt()];
        for (int i = 0; i < blocks.length; i++) {blocks[i] = new Stack<Integer>();} //initializing main array of stacks of blocks
        for (int i = 0; i < blocks.length; i++) {blocks[i].push(i);} //add first block to each stack
        Stack retainer = new Stack<Integer>(); //used for when moving stacks of blocks instead of one block.

        boolean m; //move or pile
        boolean on; //onto or over

        int fromBlock; //block being moved
        int toBlock; //block where the fromBlock is being moved

        String command = input.next();
        while (!command.equals("quit"))
        {
            m = command.equals("move");
            fromBlock = input.nextInt();
            on = input.next().equals("onto");
            toBlock = input.nextInt();

            if (m) //put back blocks on fromBlock
            {
                if (on) //put back blocks on toBlock
                {
                    int holder = blocks[fromBlock].pop().intValue(); //I get a compiler error here
                    moveOnto(blocks, holder, toBlock);
                }
                else //fromBlock goes on top of stack on toBlock
                {
                }
            }
            else //bring blocks on fromBlock
            {
                if (on) //put back blocks on toBlock
                {
                }
                else //fromBlock goes on top of stack on toBlock
                {
                }
            }

            command = input.next();
        }
    }

    void moveOnto(Stack[] array, int sBlock, int rBlock)
    {

    }
}

该错误表明无法识别 .intValue()。显然这是 Integer 的一个方法，从那时起我发现它返回的是 Object 对象而不是 Integer 类型。如何让它返回整数类型？

Answer 1

要定义泛型数组，您需要执行此操作。

@SuppressWarnings("unchecked") // to avoid warnings.
Stack<Integer>[] blocks = new Stack[n];

然后你就可以写了

int holder = blocks[fromBlock].pop();

是的，它确实可以编译并且工作得很好。

编辑:为什么编译器不能让你这样做

Stack<Integer>[] blocks = new Stack<Integer>[n];

或

Stack<Integer>[] blocks = new Stack<>[n];

我无法理解同一件事的含义。