超类上受保护数组的值意外更改

Question

我正在使用 bitboards 编写一个国际象棋引擎，我想为 bitboards 初始化器创建一个可扩展的 API，这将允许我在未来添加更多变体，例如 chess960。

所以我想出了以下抽象超类，它为所有类型的初始化程序提供了一个统一的接口：它分配用于存储位板的数组，然后调用必须由任何子类实现的抽象方法 init() , 在里面应该创建位板并将其分配给相应的数组

public abstract class BitboardInitializer {
 
    private static final int NUMBER_OF_PLAYERS = 2;
 
    protected long[] pawnsPositions, knightsPositions, bishopsPositions,
            rooksPositions, queenPositions, kingPositions;
 
    protected BitboardInitializer() {
        pawnsPositions = knightsPositions = bishopsPositions =
                rooksPositions = queenPositions = kingPositions = new long[NUMBER_OF_PLAYERS];
        init();
    }
 
    protected abstract void init();
 
    public long getPawnsPositionsAs(int side) {
        return pawnsPositions[side];
    }
 
    public long getKnightsPositionsAs(int side) {
        return knightsPositions[side];
    }
 
    public long getBishopsPositionsAs(int side) {
        return bishopsPositions[side];
    }
 
    public long getRooksPositionsAs(int side) {
        return rooksPositions[side];
    }
 
    public long getQueenPositionsAs(int side) {
        return queenPositions[side];
    }
 
    public long getKingPositionsAs(int side) {
        return kingPositions[side];
    }
}

一种初始化标准国际象棋位板的实现，它只是分配硬编码的位板值，因为标准国际象棋总是以一种方式开始。 Side.White 和 Side.Black 是两个静态 final 字段，用作数组索引以避免不一致。白色 = 0，黑色 = 1：

public final class StandardChessInitializer extends BitboardInitializer {
 
    public StandardChessInitializer() {
        super();
    }
 
    protected void init() {
        pawnsPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_11111111_00000000L;
        pawnsPositions[Side.BLACK] =
                0b00000000_11111111_00000000_00000000_00000000_00000000_00000000_00000000L;
        knightsPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_01000010L;
        knightsPositions[Side.BLACK] =
                0b01000010_00000000_00000000_00000000_00000000_00000000_00000000_00000000L;
        bishopsPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00100100L;
        bishopsPositions[Side.BLACK] =
                0b00100100_00000000_00000000_00000000_00000000_00000000_00000000_00000000L;
        rooksPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_10000001L;
        rooksPositions[Side.BLACK] =
                0b10000001_00000000_00000000_00000000_00000000_00000000_00000000_00000000L;
        queenPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00010000L;
        queenPositions[Side.BLACK] =
                0b00010000_00000000_00000000_00000000_00000000_00000000_00000000_00000000L;
        kingPositions[Side.WHITE] =
                0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00001000L;
        kingPositions[Side.BLACK] =
                0b00001000_00000000_00000000_00000000_00000000_00000000_00000000_00000000L;
    }
}

问题是，通过调用任何超类的 getter 方法，我得到二进制 1000 用于白色（索引 0）和 10000000000000000000000000000000000000000000000000000000000000 用于黑色（索引 1）而不是分配价值观

非常感谢您对这种奇怪行为的解释，在此先感谢。

Answer 1

问题出在BitboardInitializer 构造函数中，您在其中初始化所有数组引用以指向同一个数组：

protected BitboardInitializer() {
    pawnsPositions = knightsPositions = bishopsPositions =
            rooksPositions = queenPositions = kingPositions = new long[NUMBER_OF_PLAYERS];
    init();
}

应该是：

protected BitboardInitializer() {
    pawnsPositions = new long[NUMBER_OF_PLAYERS];
    knightsPositions = new long[NUMBER_OF_PLAYERS];
    bishopsPositions = new long[NUMBER_OF_PLAYERS];
    rooksPositions = new long[NUMBER_OF_PLAYERS];
    queenPositions = new long[NUMBER_OF_PLAYERS];
    kingPositions = new long[NUMBER_OF_PLAYERS];
    init();
}