7.3

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Topic 7.3 Given two lines on a Cartesian plane, determine whether the two lines would intersect.

注意：考虑边界条件

方法：

1) If two lines are the same (same slope and y-intercept), they are considered to intersect.

2) If two lines are not parallel, then they intersect. Just check the slopes.

3) Don’t assume that the slope and y-intercept are integers. Understand limitations of floating point representations. Never check for equality with ==, but check if the difference is less than an epsilon value.

public class Line {static double epsilon = 0.000001;public double slope;public double y_intercept;public Line(double s, double y) {slope = s;y_intercept = y;}public boolean intersect(Line line2) {//考虑完全重合的边界条件return Math.abs(slope - line2.slope) > epsilon || Math.abs(y_intercept - line2.y_intercept) < epsilon;}public static void main(String[] args) {Line line1 = new Line(5, 9);Line line2 = new Line(5, 7);System.out.println(line1.intersect(line2));}}

//结果false