java - 在主方法中调用类的构造函数？

Question

我已经阅读了其他一些问题，但似乎仍然不知道如何让我的问题工作，感谢任何帮助。下面给出了我到目前为止的代码。我希望能够调用 newPointParameters 来创建一个新类。

public class Lab4ex1 {
public static void main(String[] args) {
    System.out.println("" + 100);

    new newPointParameter(42,24);
}
class Point {
    private double x = 1;
    private double y = 1;

    public double getx() {
        return x;
    }
    public double gety() {
        return y;
    }
    public void changePoint(double newx, double newy) {
        x = newx;
        y = newy;
    }
    public void newPointParameters(double x1, double y1) {
        this.x = x1; 
        this.y = y1;
    }
    public void newPoint() {
        this.x = 10;
        this.y = 10;
    }
    public double distanceFrom(double x2, double y2) {
        double x3 = x2 - this.x;
        double y3 = y2 - this.y; 
        double sqaureadd = (y3 * y3) + (x3 * x3);
        double distance = Math.sqrt(sqaureadd);
        return distance;
    }
}

}

Answer 1

因此，目前 newPointParameters 和 newPoint 都不是构造函数。相反，它们只是方法。为了使它们成为构造函数，它们需要与构造的类共享相同的名称

class Point {

  private double x = 1;
  private double y = 1;

  public Point() {
    this.x = 10;
    this.y = 10;
  }

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

然后，当您想创建一个新点时，只需执行以下操作

对于默认点

public class Lab4ex1 {

  public static void main(String[] args) {
    System.out.println("" + 100);

    //this will create a new Point object, and call the Point() constructor
    Point point = new Point();
}

对于带参数的点

public class Lab4ex1 {

  public static void main(String[] args) {
    System.out.println("" + 100);

    //this will create a new Point object, and call the 
    //Point(double x, double y) constructor
    Point point = new Point(10.0, 10.0);
}