使用传递给构造器的引用是否安全

Question

我有以下代码：

public class Triangle {

    private Point left;
    private Point right;
    private Point top;

    public Triangle(Point left, Point right, Point top) {
        this.left = left;
        this.right = right;
        this.top = top;
    }

    // more program logic...
}

public static void main(String[] args) {

    Point left = new Point(0.0, 1.0);
    Point right = new Point(2.4, 3.2);
    Point top = new Point(5.8, 2.0);

    Triangle t = new Triangle(left, right, top);

    top.setX(10.2);
    top.setY(23.4); 
}

public Triangle(Point left, Point right, Point top) {
    this.left = new Point(left);
    this.right = new Point(right);
    this.top = new Point(top);
}

Answer 1

您可以在构造函数中克隆原始点，并对外部世界隐藏克隆。如果Point已经实现cloneable，或者您可以自己实现它，请按以下方式使用：

public Triangle(Point left, Point right, Point top) {
    this.left = left.clone();
    this.right = right.clone();
    this.top = top.clone();
}

如果Point没有实现cloneable，并且您无法访问其源代码，只需手动克隆points：

public Triangle(Point left, Point right, Point top) {
    this.left = new Point(left.getX(), left.getY());
    this.right = new Point(right.getX(), right.getY());
    this.top = new Point(top.getX(), top.getY());
}