j_drawsin.java.bak

一个十分好的java基础学习的课件

// ////////////////////////////////////////////////////////
// 
// J_DrawSin.java
// 
// Created by Jun-Hai Yong,    on XX xx, xxxx (Date)
// ////////////////////////////////////////////////////////
// Readme:
//     Display the two-dimensional curve:
//         y=sin(x), x=[0, 2pi]
//     on a web page.
// ////////////////////////////////////////////////////////
// Using this example, please explicitly refer to the book:
//     Jun-Hai Yong. Programming in Java. 
//     Beijing: Tsinghua University Press, 2004.
// 使用本例子，请注明引用:
//     雍俊海. Java 程序设计. 北京: 清华大学出版社, 2004.
// Please note that the author and publisher make no 
// warranty of any kind on the examples provided.
// ////////////////////////////////////////////////////////

import java.awt.Graphics;
import java.applet.Applet;

// ////////////////////////////////////////////////////////
// Display y=sin(x)
public class J_DrawSin extends Applet
{
    public void paint(Graphics g)
    {
        super.paint( g ); // Call system's method.

        double d, tx;
        int    x, y, x0, y0;

        d= Math.PI/100; // The curve is divided into 200 segments
        x0=y0=0;
        for (tx= 0, x= 20; tx<= 2*Math.PI; tx+=d, x++)
        { // Draw the curve
            y= 120-(int)(Math.sin(tx)*50+60); // Scaling, translation and symmetry
            if (x>20)
                g.drawLine(x0, y0, x, y);
            x0= x;
            y0= y;
        } // End of the loop: for
        g.drawString("y=sin(x)", 10, 70);
    } // End of method: paint
} // End of class: J_DrawSin