实现直线类

 //实现直线类，通过输入一次函数的参数（a,b,c）建模直线，并且对直线进行检查，如果输入的a和b都为零的话，

//则需要重新输入，其他功能为：判断所输入的两条直线是否平行，如果平行则告知用户，

//如果不平行则将这两条直线的交点输出来。（初学者仅供参考考）

import java.io.BufferedReader;import java.io.InputStreamReader;import java.text.DecimalFormat;public class Line{private double a;private double b;private double c;Line(){a = getValue();b = getValue();c = getValue();}public double getValue(){return inputValue();}//输入数值public double inputValue(){double value = 0.0;System.out.println("Enter value:");try{BufferedReader in=new BufferedReader(new InputStreamReader(System.in));String s=in.readLine();value = Double.parseDouble(s);}catch (Exception e){}return value;}//检查输入的直线是否合法，如果不合法将循环输入public void checkLine(){while(a == 0 && b == 0){System.out.println("This isn't a line: a and b can't be 0 " +"at the same time.Please input again.");a = getValue();b = getValue();c = getValue();}System.out.println("This is a line. And input another.");}//输出直线public void displayLine(){System.out.println("line: " + a + "x + " + b + "y + " + c + " = 0.0");}//判断两条直线是否平行public void isParallel(Line l1, Line l2 ){if((l1.a == 0 && l2.b == 0 && l2.a != 0 && l1.b != 0) || (l2.a ==2 && l1.b == 0 && l1.a != 0 && l2.b != 0)){System.out.println("/nline1 and line2 aren't parallel.");pointOfIntersection(l1, l2);}else if(l1.a * l2.b == l2.a * l1.b)System.out.println("/nline1 and line2 are parallel.");else {System.out.println("/nline1 and line2 aren't parallel.");pointOfIntersection(l1, l2);}}//求交点public void pointOfIntersection(Line l1, Line l2){DecimalFormat twoDigits = new DecimalFormat("0.00");double y = 0.0;double x = 0.0;double n1 = 0.0;//若其中某个系数为零的情况if(l1.a == 0){y = (-l1.c) / l1.b;x = (-l2.c - l2.b * y) / l2.a;}else if(l2.a == 0){y = (-l2.c) / l2.b;x = (-l1.c - l1.a * y) / l1.a;}//系数都不为零的情况else{n1 = l1.a / l2.a;y = (-l1.c + n1 * l2.c) / (l1.b - n1 * l2.b);x = (-l2.c - l2.b * y) / l2.a;}System.out.println("The point of intersection is (" + twoDigits.format(x) + " , " + twoDigits.format(y) + ")");}public static void main(String[] args){System.out.println("Enter value of a, b and c about every line." +" Make sure a and b can't be 0 at the same time!!");Line line1 = new Line();line1.checkLine();Line line2 = new Line();line2.checkLine();line1.displayLine();line2.displayLine();line1.isParallel(line1, line2 );}}