java - 通过引用更新对象(数独)

Question

我有一个数独谜题求解器，需要我们使用递归。问题是我检查可用空间的 boolean 值应该通过引用更新当前位置，但事实并非如此。什么会导致这个？

    public boolean solve()
{
    Coordinate current = new Coordinate(); 

    if (findEmptyGridSlot(current)) {   // THE ERROR IS HERE **********  THIS IS SHOWING (0,0) STILL ******************

        for (int number = 1; number <= 9; number++)  
            if (canPlaceNumber(current, number)) { 
                grid[current.getRow()][current.getColumn()] = number; 

                if (solve()) 
                    return true; 

                grid[current.getRow()][current.getColumn()] = 0; 
            } return false;
    }else
        return true;

}

private boolean findEmptyGridSlot(Coordinate coordinate)
{
    boolean found = false;

    try{
        while (!found) 
        {
            if (grid[coordinate.getRow()][coordinate.getColumn()] == 0)
                found = true;
            else
                coordinate = coordinate.next(); // *****This is supposed to update the current coordinate ******
        }
    }catch (Exception e){
        //CREATE No Empty Cells Exception
    } 
    return found;
}

public Coordinate next()
{
    Coordinate result = new Coordinate(row, column);

    result.column++;
    if (result.column > MAX_COORDINATE)
    {
        result.column = MIN_COORDINATE;
        result.row++;
        if (result.row > MAX_COORDINATE) result = null;
    }

    return result;
}

Answer 1

Java 按值传递。这意味着您将获得坐标引用的副本。如果您将该副本指向一个新对象(即坐标=坐标.下一个)，您只是更改本地副本。现在，另一方面，如果您更改了变量所引用的对象的属性(例如，coordinate.x = foo 或 coordinate.setX(foo))，该属性也会发生变化对您的方法的调用者可见。