function.java

some example source of java,for beginner.inside there are a lot of sample examples

package example11;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Function extends JPanel{
  public void paint(Graphics g){
    double x0,x1,y0,xd,yd;
    double max=5.0;
    int w,h,hw,hh;
    //获取屏幕的尺寸
    w=getSize().width;
    h=getSize().height;
    hw=w/2;hh=h/2;
    //在屏幕上输出字符
    g.drawString("sin(2x)+cos(3x)",10,40);
    g.setColor(Color.red);
    g.drawString("0",hw+5,hh+12);
    g.drawString(""+max,hw-20,40);
    g.drawString(""+max,w-20,hh+12);
    //绘制X轴坐标
    g.drawLine(0,hh,w,hh);
    //绘制Y轴坐标
    g.drawLine(hw,0,hw,h);
    xd=2*max/w;//计算X增量
    yd=hh/max;//计算Y增量
    g.setColor(Color.blue);
    //使用增量绘制一小段线，最终组成曲线图形
    for (int x=0;x<w-1;x++){
//      x0=-max+x*xd;y0=f(x0)*yd;
//      x1=x0+xd;y1=f(x1)*yd;
//      g.drawLine(x,(int)(hh-y0),x+1,(int)(hh-y1));
    }
  }
  public static void main(String[] args) {
    JFrame.setDefaultLookAndFeelDecorated(true);
    //创建窗体
    JFrame frame = new JFrame("ColorChooserDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //显示窗体
    frame.pack();
    frame.setVisible(true);
  }
}