java计算两条线段交点

   3、通过两个方程式求出交点，再判断交点是不是落在两线段交点的区域中

代码：

public  static Point getCrossPoint(Lseg lsegA,Lseg lsegB){
		float x;
		float y;
		float x1=lsegA.getA().getX();
		float y1=lsegA.getA().getY();
		float x2=lsegA.getB().getX();
		float y2=lsegA.getB().getY();
		float x3=lsegB.getA().getX();
		float y3=lsegB.getA().getY();
		float x4=lsegB.getB().getX();
		float y4=lsegB.getB().getY();
		float k1=Float.MAX_VALUE;
		float k2=Float.MAX_VALUE;
		boolean flag1=false;
		boolean flag2=false;
		
		if((x1-x2)==0)
			flag1=true;
		if((x3-x4)==0)
			flag2=true;
		
		if(!flag1)
			k1=(y1-y2)/(x1-x2);
		if(!flag2)
			k2=(y3-y4)/(x3-x4);
		
		if(k1==k2)
			return null;
		
		if(flag1){
			if(flag2)
				return null;
			x=x1;
			if(k2==0){
				y=y3;
			}else{
				y=k2*(x-x4)+y4;
			}
		}else if(flag2){
			x=x3;
			if(k1==0){
				y=y1;
			}else{
				y=k1*(x-x2)+y2;
			}
		}else{
			if(k1==0){
				y=y1;
				x=(y-y4)/k2+x4;
			}else if(k2==0){
				y=y3;
				x=(y-y2)/k1+x2;
			}else{
				x=(k1*x2-k2*x4+y4-y2)/(k1-k2);
				y=k1*(x-x2)+y2;
			}			
		}
		if(between(x1,x2,x)&&between(y1,y2,y)&&between(x3,x4,x)&&between(y3,y4,y)){
			Point point=new Point();
			point.setX(x);
			point.setY(y);
			if(point.equals(lsegA.getA())||point.equals(lsegA.getB()))
				return null;
			return point;
		}else{
			return null;
		}				
	}
	
	public static boolean between(float a,float b,float target){
		if(target>=a-0.01&&target<=b+0.01||target<=a+0.01&&target>=b-0.01)
			return true;
		else
			return false;
	}}