stillclock.java

一个十分好的java基础学习的课件

// StillClock.java: Display a clock in JPanel
import java.awt.*;
import java.util.*;
import java.text.*;         
import javax.swing.*;

public class StillClock extends JPanel
{
  protected TimeZone timeZone;
  protected int xCenter, yCenter;
  protected int clockRadius;
  protected DateFormat formatter;

  // Default constructor
  public StillClock()
  {
    this(Locale.getDefault(), TimeZone.getDefault());
  }

  // Construct a clock with specified locale and time zone
  public StillClock(Locale locale, TimeZone timeZone)
  {
    setLocale(locale);
    this.timeZone = timeZone;
  }

  // Set timezone using a time zone id such as "CST"
  public void setTimeZoneID(String newTimeZoneID)
  {
    timeZone = TimeZone.getTimeZone(newTimeZoneID);
  }

  // Override the paintComponent to display a clock
  public void paintComponent(Graphics g)
  {
    super.paintComponent(g);

    // Initialize clock parameters
    clockRadius =
      (int)(Math.min(getSize().width, getSize().height)*0.7*0.5);
    xCenter = (getSize().width)/2;
    yCenter = (getSize().height)/2;

    // Draw circle
    g.setColor(Color.black);
    g.drawOval(xCenter - clockRadius,yCenter - clockRadius,
      2*clockRadius, 2*clockRadius);
    g.drawString("12",xCenter-5, yCenter-clockRadius);
    g.drawString("9",xCenter-clockRadius-10,yCenter+3);
    g.drawString("3",xCenter+clockRadius,yCenter+3);
    g.drawString("6",xCenter-3,yCenter+clockRadius+10);

    // Get current time using GregorianCalendar
    GregorianCalendar cal = new GregorianCalendar(timeZone);

    // Draw second hand
    int second = (int)cal.get(GregorianCalendar.SECOND);
    int sLength = (int)(clockRadius*0.9);
    int xSecond =
      (int)(xCenter + sLength*Math.sin(second*(2*Math.PI/60)));
    int ySecond =
      (int)(yCenter - sLength*Math.cos(second*(2*Math.PI/60)));
    g.setColor(Color.red);
    g.drawLine(xCenter, yCenter, xSecond, ySecond);

    // Draw minute hand
    int minute = (int)cal.get(GregorianCalendar.MINUTE);
    int mLength = (int)(clockRadius*0.75);
    int xMinute =
      (int)(xCenter + mLength*Math.sin(minute*(2*Math.PI/60)));
    int yMinute =
      (int)(yCenter - mLength*Math.cos(minute*(2*Math.PI/60)));
    g.setColor(Color.blue);
    g.drawLine(xCenter, yCenter, xMinute, yMinute);

    // Draw hour hand
    int hour = (int)cal.get(GregorianCalendar.HOUR_OF_DAY);
    int hLength = (int)(clockRadius*0.6);
    int xHour = (int)(xCenter +
      hLength*Math.sin((hour+minute/60.0)*(2*Math.PI/12)));
    int yHour = (int)(yCenter -
      hLength*Math.cos((hour+minute/60.0)*(2*Math.PI/12)));
    g.setColor(Color.green);
    g.drawLine(xCenter, yCenter, xHour, yHour);

    // Set display format in specified style, locale and timezone
    formatter = DateFormat.getDateTimeInstance
      (DateFormat.MEDIUM, DateFormat.LONG, getLocale());
    formatter.setTimeZone(timeZone);

    // Display current date
    g.setColor(Color.red);
    String today = formatter.format(cal.getTime());
    FontMetrics fm = g.getFontMetrics();
    g.drawString(today, (getSize().width -
    fm.stringWidth(today))/2, yCenter+clockRadius+30);
  }
}