[英]Calling a constructor from a class in the main method?
我已經閱讀了其他一些問題,但似乎仍然無法弄清楚如何使我的工作,任何幫助都值得贊賞。 我到目前為止的代碼如下。 我希望能夠調用newPointParameters創建一個新類。
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;
}
}
}
它應該是
public static void main(String[] args) {
System.out.println("" + 100);
Point p = new Point();
p.newPointParameter(42,24);
}
因此,當前,newPointParameters和newPoint都不是構造函數。 相反,它們只是方法。 為了使它們成為構造函數,它們需要與構造類共享相同的名稱。
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,當您要創建新點時,只需執行以下操作
對於默認點
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();
}
對於帶參數的點
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);
}
newPointParameters
不是構造函數。 我認為這是您要執行的操作:
public Point(double x1, double y1) {
x = x1;
y = y1;
}
然后,您可以使用以下構造函數在主類中創建Point
對象:
Point p = new Point(42, 24);
看起來您還打算將newPoint()
用作構造函數,因此應如下所示:
public Point() {
x = 10;
y = 10;
}
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