问题 1028: C语言程序设计教程（第三版）课后习题8.2

import java.text.DecimalFormat;

import java.util.Scanner;

public class Prog1028 {

public static void main(String[] args) throws Exception {

Scanner scan = new Scanner(System.in);

double a = scan.nextDouble();

double b = scan.nextDouble();

double c = scan.nextDouble();

String x1 = null;

String x2 = null;

DecimalFormat xx = new DecimalFormat("#0.000");

double p, q;

p = -b / (2 * a);

if (Math.abs(b * b - 4 * a * c) < 1.0e-6 || b * b - 4 * a * c >= 0) {

q = Math.sqrt(b * b - 4 * a * c) / (2 * b);

x1 = xx.format(p + q);

x2 = xx.format(p - q);

} else if (b * b - 4 * a * c < 0) {

q = (Math.sqrt(4 * a * c - b * b)) / (2 * a);

x1 = xx.format(p) + "+" + xx.format(q);

x2 = xx.format(p) + "-" + xx.format(q);

}

System.out.println("x1=" + x1 + "i" + " x2=" + x2 + "i");

}

}