下面这个DEMO演示了如何在Java中播放音频。

import java.io.*; import java.net.URL; import javax.sound.sampled.*; import javax.swing.*; // To play sound using Clip, the process need to be alive. // Hence, we use a Swing application. public class playSoundDemo extends JFrame { // Constructor public playSoundDemo() { this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.setTitle("Play Sound Demo"); this.setSize(300, 200); this.setVisible(true); try { URL url = this.getClass().getResource("MyAudio.wav"); AudioInputStream audioIn = AudioSystem.getAudioInputStream(url); Clip clip = AudioSystem.getClip(); clip.open(audioIn); clip.start(); } catch (UnsupportedAudioFileException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (LineUnavailableException e) { e.printStackTrace(); } } public static void main(String[] args) { new playSoundDemo(); } }导出PDF文件

将表格导出成pdf也是一个比较常见的需求。通过itextpdf，导出pdf也不是什么难事。

import java.io.FileOutputStream; import com.itextpdf.text.Document; import com.itextpdf.text.Paragraph; import com.itextpdf.text.pdf.PdfPCell; import com.itextpdf.text.pdf.PdfPTable; import com.itextpdf.text.pdf.PdfWriter; public class DrawPdf { public static void main(String[] args) throws Exception { Document document = new Document(); PdfWriter.getInstance(document, new FileOutputStream("Employee.pdf")); document.open(); Paragraph para = new Paragraph("Employee Table"); para.setSpacingAfter(20); document.add(para); PdfPTable table = new PdfPTable(3); PdfPCell cell = new PdfPCell(new Paragraph("First Name")); table.addCell(cell); table.addCell("Last Name"); table.addCell("Gender"); table.addCell("Ram"); table.addCell("Kumar"); table.addCell("Male"); table.addCell("Lakshmi"); table.addCell("Devi"); table.addCell("Female"); document.add(table); document.close(); } }邮件发送

在Java中发送邮件也很简单。你只需装一下Java Mail这个jar包，放到你的类路径里即可。在下面的代码中，我们设置了几个基础属性，然后便可以发送邮件了：

import java.util.*; import javax.mail.*; import javax.mail.internet.*; public class SendEmail { public static void main(String [] args) { String to = "[email protected]"; String from = "[email protected]"; String host = "localhost"; Properties properties = System.getProperties(); properties.setProperty("mail.smtp.host", host); Session session = Session.getDefaultInstance(properties); try{ MimeMessage message = new MimeMessage(session); message.setFrom(new InternetAddress(from)); message.addRecipient(Message.RecipientType.TO,new InternetAddress(to)); message.setSubject("My Email Subject"); message.setText("My Message Body"); Transport.send(message); System.out.println("Sent successfully!"); } catch (MessagingException ex) { ex.printStackTrace(); } } }计算时间

许多程序都需要精确的时间计量。Java提供了一个System的静态方法来支持这一功能：

currentTimeMillis()：返回当前时间自新纪元时间以来的毫秒值，long类型。

long startTime = System.currentTimeMillis(); long estimatedTime = System.currentTimeMillis() - startTime;

nanoTime()：返回系统计时器当前的精确时间，纳秒值，这也是long类型。nanoTime()主要是用于计算相对时间而非绝对时间。

long startTime = System.nanoTime(); long estimatedTime = System.nanoTime() - startTime;图片缩放

图片缩放可以通过AffineTransform来完成。首先要生成一个输入图片的图片缓冲，然后通过它来渲染出缩放后的图片。

import java.awt.Graphics2D; import java.awt.geom.AffineTransform; import java.awt.image.BufferedImage; import java.io.File; import javax.imageio.ImageIO; public class RescaleImage { public static void main(String[] args) throws Exception { BufferedImage imgSource = ImageIO.read(new File("images//Image3.jpg")); BufferedImage imgDestination = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB); Graphics2D g = imgDestination.createGraphics(); AffineTransform affinetransformation = AffineTransform.getScaleInstance(2, 2); g.drawRenderedImage(imgSource, affinetransformation); ImageIO.write(imgDestination, "JPG", new File("outImage.jpg")); } }捕获鼠标动作

实现了MouseMotionListner接口后，便可以捕获鼠标事件了。 当鼠标进入到某个特定区域时便会触发MouseMoved事件，你便能捕获到这个移动的动作了。通过一个例子来看下：

import java.awt.event.*; import javax.swing.*; public class MouseCaptureDemo extends JFrame implements MouseMotionListener { public JLabel mouseHoverStatus; public static void main(String args[]) { new MouseCaptureDemo(); } MouseCaptureDemo() { setSize(500, 500); setTitle("Frame displaying Coordinates of Mouse Motion"); mouseHoverStatus = new JLabel("No Mouse Hover Detected.", JLabel.CENTER); add(mouseHoverStatus); addMouseMotionListener(this); setVisible(true); } public void mouseMoved(MouseEvent e) { mouseHoverStatus.setText("Mouse Cursor Coordinates => X:"+e.getX()+" | Y:"+e.getY()); } public void mouseDragged(MouseEvent e) {} }FileOutputStream Vs. FileWriter

在Java中有两种写文件的方式：FileOutputStream与FileWriter。开发人员经常会在它们之间犹豫不决。下面这个例子能帮忙你更好地理解在不同的场景下应该选择何种方案。首先我们来看一下实现：