fc.java

该JAVA程序是求出一元二次方程的解

import javax.swing.JOptionPane;

public class Fc
{
	public static void main(String args[])
	{
		
		double a;
        double b;
        double c;
        String result;
        a = Double.parseDouble(JOptionPane.showInputDialog("请输入参数a的值"));
		b = Double.parseDouble(JOptionPane.showInputDialog("请输入参数b的值"));
		c = Double.parseDouble(JOptionPane.showInputDialog("请输入参数c的值"));
		
        if(a==0)
		{
			if(b==0)
			{
				result = "输入出现错误！";
			}
			else
			{
			
			result = "该方程有一个实数根：\nx="+Math.round(-c/b*1000)/1000.00;
			}
		}
		else
		{
			double d;
			d = b*b-4*a*c;
			if(d==0)
			{
				double x;
				
				x = Math.round(-b/2/a*1000)/1000.00;
				result = "该方程有两个相等的实数根：\nx1=x2="+x;
			}
			
			else if(d>0)
			{
				double x1;
				double x2;
				
				x1 = Math.round((-b+Math.sqrt(d))/2/a*1000)/1000.00;
				x2 = Math.round((-b-Math.sqrt(d))/2/a*1000)/1000.00;
				result = "该方程有两个不相等的实数根：\nx1="+x1+"\nx2="+x2;
			}
			
			else
			{
				String x1;
				String x2;
			
				x1 = Math.round(-b/2/a*1000)/1000.00
					+"+"
					+Math.round(Math.sqrt(-d)/2/a*1000)/1000.00
					+"i";
				x2 = Math.round(-b/2/a*1000)/1000.00
					+"-"
					+Math.round(Math.sqrt(-d)/2/a*1000)/1000.00
					+"i";
				result = "该方程有两个不相等的复数根：\nx1="+x1+"\nx2="+x2;
			}
		}
		
		JOptionPane.showMessageDialog(null, result, "结果", JOptionPane.INFORMATION_MESSAGE);
		
		System.exit(0);
	}
}