a3.java

来自「初学java,最近帮同学作的一些实验」· Java 代码 · 共 40 行

package mypackage;
import java.util.Scanner;
public class A3 implements computer,inputer{
	    int a,b,c,d;
	    double x1,x2,x0;
	    public void input()
	    {
	    	System.out.print("请输入一元三次方程的系数a,b,c,d:" );
	    	Scanner cin=new Scanner(System.in);
	    	a=cin.nextInt();
	    	b=cin.nextInt();
	    	c=cin.nextInt();
	    	d=cin.nextInt();
	    	do
	    	{  System.out.print("请输入根的范围:x1--x2:" );
	    	   x1=cin.nextDouble();
	    	   x2=cin.nextDouble();
	    	}while(prepare(x1)*prepare(x2)>=0);
	    	
	    }
	    public void comput()
	    {
	    	do
	    	{
	    		x0=(x1+x2)/2;
	    		if(prepare(x0)*prepare(x1)<0)
	    		    x2=x0;
	    		else
	    			x1=x0;
	    	}while(Math.abs(prepare(x0))>=0.000005);
	    	System.out.print("该范围内该方程的近似根为: "+x0 );
	    }
	    public double prepare(double x)
	    {
	    	double fx=a*Math.pow(x,3)+b*Math.pow(x,2)+c*x+d;
	    	return fx;
	    }

}