Java基础语法实战系统总结2（陆续上传中...）

利用Java API,查找到Math类，求一元二次方程？提示用Math类中的开方sqrt，求幂pow等等。SolveQuadratic.java
/** 求解二次方程 a*x*x+b*x+c=0
* b*b-4*a*c=0, 有两个相等实根
* b*b-4*a*c>0, 有两个相异实根
* b*b-4*a*c<0, 有两个共轭复根
*/
import javax.swing.*;
public class SolveQuadratic{
public static void main(String[] args){
if(args.length!=3){
System.out.println("Usage: java SolveQuadratic aCoef bCoef cCoef");
System.out.println("Example: java SolveQuadratic 1 2 1");
System.exit(-1);
}
double a;
double b;
double c;
a=Double.parseDouble(args[0]);
if(Math.abs(a) System.out.println("a=0, not a Quadratic");
System.exit(-1);
}
b=Double.parseDouble(args[1]);
c=Double.parseDouble(args[2]);
System.out.println("Quadratic is "+a+"*x*x+"+b+"*x+"+c+"=0");

double disc=b*b-4*a*c;

if(Math.abs(disc) System.out.println("The Quadratic has two equal roots:"+(-b/(2*a)));
}else if(disc>Math.pow(10,-6)){ //disc大于0
double root1=(-b+Math.sqrt(disc))/(2*a);
double root2=(-b-Math.sqrt(disc))/(2*a);
System.out.println("The Quadratic has two distinct roots:"+root1+" "+root2);
}else{//disc小于0
double realPart=-b/(2*a);
double imagPart=Math.sqrt(-disc)/(2*a);
System.out.println("The Quadratic has complex roots:");
System.out.println(realPart+"+"+imagPart+"i");
System.out.println(realPart+"-"+imagPart+"i");
}
}
}