java 图形编程常用的，检验两条直线是否相交的java算法.zip

import java.awt.*; public class LineCrossing { double Ax, Bx, Cx, Dx, Px, Ay, By, Cy, Dy, Py, d1x, d2x, d1y, d2y; public LineCrossing(Point A, Point B, Point C, Point D) { Ax = A.getX(); Ay = A.getY(); Bx = B.getX(); By = B.getY(); d1x = Bx - Ax; d1y = By - Ay; Cx = C.getX(); Cy = C.getY(); Dx = D.getX(); Dy = D.getY(); d2x = Dx - Cx; d2y = Dy - Cy; } // returns true if the lines AB and CD cross public boolean LinesCross() { boolean result = false; crossingPoint(); // ^ is exclusive or - e.g. either Px is less than Ax or Bx but not both boolean xABok = (Px < Ax) ^ (Px < Bx ); // Px is between Ax and Bx boolean xCDok = (Px < Cx) ^ (Px < Dx ); // Py is between Ay and By boolean yABok = (Py < Ay) ^ (Py < By ); // Px is between Cx and Dx boolean yCDok = (Py < Cy) ^ (Py < Dy ); // Py is between Cy and Dy result = xABok && xCDok && yABok && yCDok ; return result; } // sets Px, Py to the crossing point of the two lines // it works by getting P to be on both lines // if they're parallel it still works, but returns infinity public void crossingPoint( ) { double denom = d1x * d2y - d2x * d1y; Py = ((Cx*Dy-Cy*Dx)*d1y - (Ax*By - Ay*Bx)*d2y)/denom; Px = ((Cx*Dy-Cy*Dx)*d1x - (Ax*By - Ay*Bx)*d2x)/denom; System.out.println(" " + Px + ", " + Py); } }