JAVA计算两条直线的交点（判断两条线段相交）

//计算两条直线的交点
//输入四个点，前两个点确定线段1，后两个点确定线段2
//输出交点坐标
public class Main{
    public static void main(String args[]){
        double[] point1= new double[]{10.0,29.0};
        double[] point2 = new double[]{1.0,3.0};

        double[] point3 = new double[]{40,2};
        double[] point4 = new double[]{90,3};
        double[] node = cross(point1,point2,point3,point4);
        if(node==null)System.out.println(false);
        else System.out.println(node[0]+","+node[1]);
        HashSet set = new HashSet<>();
        set.add(node[0]+":"+node[1]);
        for(String item:set){
            System.out.println(item);
        }
    }

    public static double[] cross(double[] point1,double[] point2,double[] point3,double[] point4){
        if((point2[1]-point1[1])*(point4[0]-point3[0])==(point4[1]-point3[1])*(point2[0]-point1[0]))return null;
        if(point2[0]-point1[0]==0){
            double k2 = (point4[1]-point3[1])/(point4[0]-point3[0]);
            double b2 = point3[1]-point3[0]*k2;
            double cross_x = point1[0];
            double cross_y = k2*cross_x+b2;
            return new double[]{cross_x,cross_y};
        }
        if(point4[0]-point3[0]==0){
            double k1 = (point2[1]-point1[1])/(point2[0]-point1[0]);
            double b1 = point1[1]-point1[0]*k1;
            double cross_x = point3[0];
            double cross_y = k1*cross_x+b1;
            return new double[]{cross_x,cross_y};
        }
        double k1 = (point2[1]-point1[1])/(point2[0]-point1[0]);
        double b1 = point1[1]-point1[0]*k1;
        double k2 = (point4[1]-point3[1])/(point4[0]-point3[0]);
        double b2 = point3[1]-point3[0]*k2;
        double cross_x = (b1-b2)/(k2-k1);
        double cross_y = k1*cross_x+b1;
        return new double[]{cross_x,cross_y};
    }
}