java实现一个直线类继承于图形抽象类，属性有：起点和终点，功能是计算长度

public abstract class Shape {
public abstract double calculateArea();
public abstract double calculatePerimeter();
}

public class Line extends Shape {
private Point startPoint;
private Point endPoint;

public Line(Point startPoint, Point endPoint) {
this.startPoint = startPoint;
this.endPoint = endPoint;
}

public Point getStartPoint() {
return startPoint;
}

public Point getEndPoint() {
return endPoint;
}

public void setStartPoint(Point startPoint) {
this.startPoint = startPoint;
}

public void setEndPoint(Point endPoint) {
this.endPoint = endPoint;
}

@Override
public double calculateArea() {
return 0;
}

@Override
public double calculatePerimeter() {
return startPoint.distance(endPoint);
}
}

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

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

public double getX() {
return x;
}

public double getY() {
return y;
}

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

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

public double distance(Point otherPoint) {
double dx = x - otherPoint.getX();
double dy = y - otherPoint.getY();
return Math.sqrt(dx * dx + dy * dy);
}
}