java编程判断这两条直线是否相交？，若相交，求出交点。

Question

从键盘输入8个整数，分别表示平面上四个点，即A（X1，Y1），B（X2，Y2），C（X3，Y3）D（X4，Y4），其中0<=Xi，Yi<=1000，前两个点AB和后两个点CD分别确定一条直线，判断这两条直线是否相交？，若相交，求出交点。

要求：
1、构建一个点Point类，包含两个成员变量X，Y，其中X表示横坐标，Y表示纵坐标
2、构建一个直线Line类，包含两个成员变量A，B（其中A、B分别表示平面上的点）和一个为这两个点赋值的构造方法。
3、构建一个相交LineIntersect类，包含两个成员变量AB，CD（其中AB、CD分别表示平面上的直线）和名为JudgeLineIntersect的方法：判断这两条直线是否相交？，若相交，求出交点。
提示：
　　如果两条直线重合，则输出“两条直线重合”
如果两条直线平行，则输出“两条直线平行”
　如果两条直线相交，则计算并输出它们的交点。

判断方法
d1=(y2-y1)*(x4-x3);//判断两条直线斜率是否相等，和斜率不存在时判断两直线是否平行
d2=(x2-x1)*(y4-y3); //如果d1==d2，则平行
d3=(y3-y1)*(x2-x1);//判断两条直线是否重合
d4=(x3-x1)*(y2-y1); //如果d3==d4，则重合

Answer 1

您好，下面是我写的代码，麻烦看一下是否符合要求。

Point类：

public class Point {

    private int x;

    private int y;

    public int getX() {

        return x;

    }

    public void setX(int x) {

        this.x = x;

    }

    public int getY() {

        return y;

    }

    public void setY(int y) {

        this.y = y;

    }

}

Line类：

public class Line {

    private Point a;

    private Point b;

    public Point getA() {

        return a;

    }

    public Point getB() {

        return b;

    }

    public Line(Point a, Point b) {

        this.a = a;

        this.b = b;

    }

}

LineIntersect类：

public class LineIntersect {

    private Line ab;

    private Line cd;

    public LineIntersect(Line ab, Line cd) {

        this.ab = ab;

        this.cd = cd;

    }

    public void JudgeLineIntersect() {

        Point A = this.ab.getA();

        Point B = this.ab.getB();

        Point C = this.cd.getA();

        Point D = this.cd.getB();

        int d1 = (B.getY() - A.getY()) * (D.getX() - C.getX());

        int d2 = (B.getX() - A.getX()) * (D.getY() - C.getY());

        int d3 = (C.getY() - A.getY()) * (B.getX() - A.getX());

        int d4 = (C.getX() - A.getX()) * (B.getY() - A.getY());

        if (d1 == d2) {

            System.out.println("两条直线平行。");

        } else if (d3 == d4) {

            System.out.println("两条直线重合。");

        } else {

            System.out.println("两条直线相交。");

            int d5 = C.getY() * D.getX() - C.getX() * D.getY();

            int d6 = A.getY() * B.getX() - A.getX() * B.getY();

            float intersect_x = ((C.getX() - D.getX()) * d6 - (A.getX() - B.getX()) * d5)

                    / ((B.getY() - A.getY()) * (D.getX() - C.getX()) - (B.getX() - A.getX()) * (D.getY() - C.getY()));

            float intersect_y = ((C.getY() - D.getY()) * d6 - (A.getY() - B.getY()) * d5)

                    / ((B.getY() - A.getY()) * (D.getX() - C.getX()) - (B.getX() - A.getX()) * (D.getY() - C.getY()));

            System.out.println("交点的X坐标为：" + intersect_x);

            System.out.println("交点的Y坐标为：" + intersect_y);

        }

    }

}

下面是主类（测试类）：

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        System.out.print("请输入A点的X坐标：");

        Scanner inAX = new Scanner(System.in);

        int ax = inAX.nextInt();

        System.out.print("请输入A点的Y坐标：");

        Scanner inAY = new Scanner(System.in);

        int ay = inAY.nextInt();

        System.out.print("请输入B点的X坐标：");

        Scanner inBX = new Scanner(System.in);

        int bx = inBX.nextInt();

        System.out.print("请输入B点的Y坐标：");

        Scanner inBY = new Scanner(System.in);

        int by = inBY.nextInt();

        System.out.print("请输入C点的X坐标：");

        Scanner inCX = new Scanner(System.in);

        int cx = inCX.nextInt();

        System.out.print("请输入C点的Y坐标：");

        Scanner inCY = new Scanner(System.in);

        int cy = inCY.nextInt();

        System.out.print("请输入D点的X坐标：");

        Scanner inDX = new Scanner(System.in);

        int dx = inDX.nextInt();

        System.out.print("请输入D点的Y坐标：");

        Scanner inDY = new Scanner(System.in);

        int dy = inDY.nextInt();

        Point A = new Point();

        A.setX(ax);

        A.setY(ay);

        Point B = new Point();

        B.setX(bx);

        B.setY(by);

        Point C = new Point();

        C.setX(cx);

        C.setY(cy);

        Point D = new Point();

        D.setX(dx);

        D.setY(dy);

        Line AB = new Line(A, B);

        Line CD = new Line(C, D);

        LineIntersect lineIntersect = new LineIntersect(AB, CD);

        lineIntersect.JudgeLineIntersect();

        inAX.close();

        inAY.close();

        inBX.close();

        inBY.close();

        inCX.close();

        inCY.close();

        inDX.close();

        inDY.close();

    }

}

下面是我刚才做的测试结果：

Answer 2

您好，下面是我写的代码，麻烦看一下是否符合要求。Point类：public class Point {
private int x; private int y; public int getX() { return x; } public void setX(int x) { this.x = x; } public int getY() { return y; } public void setY(int y) { this.y = y; }}Line类：public class Line {
private Point a; private Point b; public Point getA() { return a; } public Point getB() { return b; } public Line(Point a, Point b) { this.a = a; this.b = b; }}LineIntersect类：public class LineIntersect { private Line ab; private Line cd; public LineIntersect(Line ab, Line cd) { this.ab = ab; ***.cd = cd; } public void JudgeLineIntersect() { Point A = this.ab.getA(); Point B = this.ab.getB(); Point C = ***.cd.getA(); Point D = ***.cd.getB(); int d1 = (B.getY() - A.getY()) * (D.getX() - C.getX()); int d2 = (B.getX() - A.getX()) * (D.getY() - C.getY()); int d3 = (C.getY() - A.getY()) * (B.getX() - A.getX()); int d4 = (C.getX() - A.getX()) * (B.getY() - A.getY()); if (d1 == d2) { System.out.println("两条直线平行。"); } else if (d3 == d4) { System.out.println("两条直线重合。"); } else { System.out.println("两条直线相交。"); int d5 = C.getY() * D.getX() - C.getX() * D.getY(); int d6 = A.getY() * B.getX() - A.getX() * B.getY(); float intersect_x = ((C.getX() - D.getX()) * d6 - (A.getX() - B.getX()) * d5) / ((B.getY() - A.getY()) * (D.getX() - C.getX()) - (B.getX() - A.getX()) * (D.getY() - C.getY())); float intersect_y = ((C.getY() - D.getY()) * d6 - (A.getY() - B.getY()) * d5) / ((B.getY() - A.getY()) * (D.getX() - C.getX()) - (B.getX() - A.getX()) * (D.getY() - C.getY())); System.out.println("交点的X坐标为：" + intersect_x); System.out.println("交点的Y坐标为：" + intersect_y); } }}下面是主类（测试类）：import java.util.Scanner;
public class Main { public static void main(String[] args) { System.out.print("请输入A点的X坐标："); Scanner inAX = new Scanner(***.in); int ax = inAX.nextInt(); System.out.print("请输入A点的Y坐标："); Scanner inAY = new Scanner(***.in); int ay = inAY.nextInt(); System.out.print("请输入B点的X坐标："); Scanner inBX = new Scanner(***.in); int bx = inBX.nextInt(); System.out.print("请输入B点的Y坐标："); Scanner inBY = new Scanner(***.in); int by = inBY.nextInt(); System.out.print("请输入C点的X坐标："); Scanner inCX = new Scanner(***.in); int cx = inCX.nextInt(); System.out.print("请输入C点的Y坐标："); Scanner inCY = new Scanner(***.in); int cy = inCY.nextInt(); System.out.print("请输入D点的X坐标："); Scanner inDX = new Scanner(***.in); int dx = inDX.nextInt(); System.out.print("请输入D点的Y坐标："); Scanner inDY = new Scanner(***.in); int dy = inDY.nextInt(); Point A = new Point(); A.setX(ax); A.setY(ay); Point B = new Point(); B.setX(bx); B.setY(by); Point C = new Point(); C.setX(cx); C.setY(cy); Point D = new Point(); D.setX(dx); D.setY(dy); Line AB = new Line(A, B); Line CD = new Line(C, D); LineIntersect lineIntersect = new LineIntersect(AB, CD); lineIntersect.JudgeLineIntersect(); inAX.close(); inAY.close(); inBX.close(); inBY.close(); inCX.close(); inCY.close(); inDX.close(); inDY.close(); }}下面是我刚才做的测试结果：