Question

使用简单的Java Point类，我希望将X和Y值限制为双精度数，必须在-10到10之间，包括-10和10。我已经编写了一些代码，但是自从我编写java以来已经有好几年了，我想知道这是用现代Java编写的：

public class Point {
    private double x;
    private double y;

    public Point(double x, double y) {
        constrain("x", x);
        constrain("y", y);
        this.x = x;
        this.y = y;
    }

    // is there a cleaner/shorter way of handling this, such as a direct way of declaring a
    // subtype of double that I could use in method signatures?
    protected static void constrain(String name, double val) {
        if ( val < -10 || val > 10 ) {
            throw new IllegalArgumentException(name + " must be between -10 and 10");
        }
    }

    public double getX() { return x; }

    public void setX(double x) {
        constrain("x", x);
        this.x = x;
    }

    public double getY() { return y; }

    public void setY(double y) {
        constrain("y", y);
        this.y = y;
    }

    @Override
    public String toString() {
        return ("[" + x + "," + y + "]"); 
    }
}

Answer 1

这可能是我做的：

public class Point
{

    private static final double X_MIN = -10.0, X_MAX = 10.0;
    private static final double Y_MIN = -10.0, Y_MAX = 10.0;

    private double x, y;

    public Point(double x, double y) throws IllegalArgumentException
    {
        setX(x);
        setY(y);
    }

    public double getX()
    {
        return x;
    }

    public double getY()
    {
        return y;
    }

    public void setX(double x) throws IllegalArgumentException
    {
        if (x < X_MIN || x > X_MAX)
        {
            throw new IllegalArgumentException("X out of range.");
        }

        this.x = x;
    }

    public void setY(double y) throws IllegalArgumentException
    {
        if (y < Y_MIN || y > Y_MIN)
        {
            throw new IllegalArgumentException("Y out of range");
        }

        this.y = y;
    }

    @Override
    public String toString()
    {
        return String.format("[%.1f,%.1f]", x, y);
    }
}

Answer 2

如果X和Y值始终来自同一个域，那么您可以将它们封装在一个为您进行检查的类中：

class Coord {
    private final double scalarValue;
    public Coord(double scalarValue) throws IllegalArgumentException {
        if (Math.abs(scalarValue) > MAX_COORD) {
            throw new IllegalArgumentException("Coordinate out of range");
        }
        this.scalarValue = scalarValue;
    }
    public double getScalar() {
        return scalarValue;
    }
}

将检查放在一个位置，并允许您在将来扩展坐标功能而不会弄乱您的Point类。它还明确地使坐标不可变，这可能是一个好主意（取决于用例）。

然后你的点构造函数变为：

public Point(Coord x, Coord y);

惯用Java：约束数据

2 个答案: