我正在实施一个国际象棋引擎，所以我构建了以下函数来测试引擎的AI部分可能的移动（实际上没有制作）。
该函数将侧面（黑色或白色）作为参数，一个类型板的对象，其中包含棋盘的所有部分的arraylist以及一些其他信息以及作为字符串的移动的源和目标方块。
我的问题是移动没有正确“制作”。我的意思是在完成此功能后返回的棋盘对象中，即使函数更改它们，碎片也没有更改的行或列。如果从中取出一块，则该板仅会改变。
public Board doTestMove(int side,Board b, String srcSq, String destSq) {
//check source square notation for validity
if (checkSqValidity(srcSq)) {
//check destination square notation for validity
if (checkSqValidity(destSq)) {
//find the piece based on the source square notation.
Piece piece =new Piece(b.notationToPiece(srcSq));
if(piece==null){
System.out.println("The piece is null");
}
//make sure the piece is owned by the player
if (piece.getColor()==side) {
//get all movements that are allowed for the selected piece
ArrayList<ArrayList<Integer>> legalMoves=new ArrayList<ArrayList<Integer>>();
legalMoves = possiblePieceMoves(piece, false);
//array coordinates for new destination
Index newLoc = new Index(b.notationToIndex(destSq).getX(),b.notationToIndex(destSq).getY());
//find out if destination location is included in the legal moves list
ArrayList<Integer> x = legalMoves.get(0); //list of row numbers
ArrayList<Integer> y = legalMoves.get(1); //list of column numbers
ListIterator<Integer> xList = x.listIterator(); //row iterator
ListIterator<Integer> yList = y.listIterator(); //column iterator
int xL, yL;
while (xList.hasNext() && yList.hasNext()) { //while lists have coordinates
//listiterator next() method doesn't work inside if statement -> assign to variables
xL = xList.next();
yL = yList.next();
if (newLoc.getX()==xL && newLoc.getY()==yL) { //legal move
b.removePiece(newLoc.getX(), newLoc.getY()); //remove captured piece from the board
piece.setRow(newLoc.getX()); //change piece row
piece.setCol(newLoc.getY()); //change piece column
b.updateGameState(); //populate the board with new location of pieces.
//place source and destination square to history of moves
if (side==0) { //if white
getHistoryOfMoves().addWhiteMove(srcSq, destSq); //add white piece move to history
} else if (side==1) { //if black
getHistoryOfMoves().addBlackMove(srcSq, destSq); //add black piece move to history
}
//promote pawns to queens if they reach enemy's end
b.promotePawnsToQueen(side);
return new Board(b); //move successful
}
}
}
} else {
System.out.println("Not a valid destination square. ");
}
} else {
System.out.println("Not a valid source notation.");
}
return null;
}
如您所见，对象块定义如下：
Piece piece =new Piece(b.notationToPiece(srcSq));
我已经得出结论，我必须将其更改为：
Piece piece =b.notationToPiece(srcSq);
在认为唯一正确发生的事情就是删除一块。因此，将某些东西直接更改为要返回的棋盘会有效。
所以我决定函数所做的更改必须影响作为对象b的arraylist的一部分而不是某个新对象的部分。
然而，当我尝试这样做时，我得到错误：
java.lang.NullPointerException
行：
if (piece.getColor()==side) {
这很奇怪，因为这个用于测试移动的函数几乎与我用于进行移动的函数（工作正常）完全相同，如下所示：
public boolean doMove(Player player, String srcSq, String destSq) {
//check source square notation for validity
if (checkSqValidity(srcSq)) {
//check destination square notation for validity
if (checkSqValidity(destSq)) {
//find the piece based on the source square notation.
Piece piece = getBoard().notationToPiece(srcSq);
//make sure the piece is owned by the player
if (piece.getColor()==player.getSide()) {
//get all movements that are allowed for the selected piece
ArrayList<ArrayList<Integer>> legalMoves = possiblePieceMoves(piece, false);
//array coordinates for new destination
Index newLoc = getBoard().notationToIndex(destSq);
//find out if destination location is included in the legal moves list
ArrayList<Integer> x = legalMoves.get(0); //list of row numbers
ArrayList<Integer> y = legalMoves.get(1); //list of column numbers
ListIterator<Integer> xList = x.listIterator(); //row iterator
ListIterator<Integer> yList = y.listIterator(); //column iterator
int xL, yL;
while (xList.hasNext() && yList.hasNext()) { //while lists have coordinates
xL = xList.next();
yL = yList.next();
if (newLoc.getX()==xL && newLoc.getY()==yL) { //legal move
getBoard().removePiece(newLoc.getX(), newLoc.getY()); //remove captured piece from the board
piece.setRow(newLoc.getX()); //change piece row
piece.setCol(newLoc.getY()); //change piece column
//place source and destination square to history of moves
if (player.getSide()==0) { //if white
getHistoryOfMoves().addWhiteMove(srcSq, destSq); //add white piece move to history
} else if (player.getSide()==1) { //if black
getHistoryOfMoves().addBlackMove(srcSq, destSq); //add black piece move to history
}
//promote pawns to queens if they reach enemy's end
getBoard().promotePawnsToQueen(player.getSide());
return true; //move successful
}
}
}
} else {
System.out.println("Not a valid destination square. ");
}
} else {
System.out.println("Not a valid source notation.");
}
return false; //move failed, not own piece
}
我找不到问题的根源。
答案 0 :(得分：0)
你的notationToPiece（）方法根据输入到该方法的srcSq字符串返回一个null Piece对象。我怀疑你的错误就在那里。