halfsearch1.java

数值算法例子,牛顿插值,拉格朗日,三次样条

/*@author 邱宇峰 ,software project031
 *2004,10,6
 */
import java.math.*;
import java.awt.*;
import java.awt.event.*;

public class halfSearch1{
	void search(Graphics g){
		//repaint();
		int x=0;
		double X,Y;
		g.drawLine(50,300,450,300);
		g.drawLine(250,150,250,300);
		g.drawString("0",250,310);
		g.drawString("1.57",407,310);
		g.drawString("-1.57",73,310);	
		for(X=-2;X<=2;X+=0.01){
			Y=100*Math.sin(X);
			g.drawString(".",50+x,300-(int)Y);
			x++;
		}	
			double a=-2,b=2,e=0.00001;
			while(b-a>e){
				X=(a+b)/2;
					if((a-2*Math.sin(a))*(X-2*Math.sin(X))<0) b=X;
					else a=X;
					g.setColor(Color.blue);
					g.drawLine(250+(int)(100*a),300,250+(int)(100*a),300-(int)(100*Math.sin(a)));
					g.drawLine(250-(int)(100*a),300,250-(int)(100*a),300+(int)(100*Math.sin(a)));
					g.setColor(Color.yellow);
					g.drawLine(250+(int)(100*b),300,250+(int)(100*b),300-(int)(100*Math.sin(b)));
					g.drawLine(250-(int)(100*b),300,250-(int)(100*b),300+(int)(100*Math.sin(b)));	
					if(Math.abs(X-2*Math.sin(X))<0.00001){
						g.setColor(Color.red);
						g.drawString("。",250+(int)(100*X),300-(int)(100*Math.sin(X)));
						g.drawString("。",250-(int)(100*X),300+(int)(100*Math.sin(X)));
					}
					for(int i=0;i<50000000;i++);
					g.setColor(Color.white);
					g.drawLine(250+(int)(100*a),300,250+(int)(100*a),300-(int)(100*Math.sin(a)));
					g.drawLine(250-(int)(100*a),300,250-(int)(100*a),300+(int)(100*Math.sin(a)));
					g.drawLine(250+(int)(100*b),300,250+(int)(100*b),300-(int)(100*Math.sin(b)));
					g.drawLine(250-(int)(100*b),300,250-(int)(100*b),300+(int)(100*Math.sin(b)));
			}
		}

	}