public class InetAddressTest
{
	public static void main(String[] args)
		throws Exception
	{
		// 根据主机名来获取对应的InetAddress实例
		InetAddress ip = InetAddress.getByName("www.crazyit.org");
		// 判断是否可达
		System.out.println("crazyit是否可达：" + ip.isReachable(2000)); 
		// 获取该InetAddress实例的IP字符串
		System.out.println(ip.getHostAddress());
		// 根据原始IP地址来获取对应的InetAddress实例
		InetAddress local = InetAddress.getByAddress(
			new byte[]{127,0,0,1});
		System.out.println("本机是否可达：" + local.isReachable(5000)); 
		// 获取该InetAddress实例对应的全限定域名
		System.out.println(local.getCanonicalHostName());
	}
}

public class URLDecoderTest
{
	public static void main(String[] args) 
		throws Exception
	{

		String keyWord = URLDecoder.decode(
			"%B7%E8%BF%F1java", "GBK");
		System.out.println(keyWord);

		String urlStr = URLEncoder.encode(
			"疯狂java讲义" , "GBK");
		System.out.println(urlStr);
	}
}

public class DownUtil
{
	// 定义下载资源的路径
	private String path;
	// 指定所下载的文件的保存位置
	private String targetFile;
	// 定义需要使用多少线程下载资源
	private int threadNum;
	// 定义下载的线程对象
	private DownThread[] threads;
	// 定义下载的文件的总大小
	private int fileSize;

	public DownUtil(String path, String targetFile, int threadNum)
	{
		this.path = path;
		this.threadNum = threadNum;
		// 初始化threads数组
		threads = new DownThread[threadNum];
		this.targetFile = targetFile;
	}

	public void download() throws Exception
	{
		URL url = new URL(path);
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		conn.setConnectTimeout(5 * 1000);
		conn.setRequestMethod("GET");
		conn.setRequestProperty(
			"Accept",
			"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
			+ "application/x-shockwave-flash, application/xaml+xml, "
			+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
			+ "application/x-ms-application, application/vnd.ms-excel, "
			+ "application/vnd.ms-powerpoint, application/msword, */*");
		conn.setRequestProperty("Accept-Language", "zh-CN");
		conn.setRequestProperty("Charset", "UTF-8");
		conn.setRequestProperty("Connection", "Keep-Alive");
		// 得到文件大小
		fileSize = conn.getContentLength();
		conn.disconnect();
		int currentPartSize = fileSize / threadNum + 1;
		RandomAccessFile file = new RandomAccessFile(targetFile, "rw");
		// 设置本地文件的大小
		file.setLength(fileSize);
		file.close();
		for (int i = 0; i < threadNum; i++)
		{
			// 计算每条线程的下载的开始位置
			int startPos = i * currentPartSize;
			// 每个线程使用一个RandomAccessFile进行下载
			RandomAccessFile currentPart = new RandomAccessFile(targetFile,
				"rw");
			// 定位该线程的下载位置
			currentPart.seek(startPos);
			// 创建下载线程
			threads[i] = new DownThread(startPos, currentPartSize,
				currentPart);
			// 启动下载线程
			threads[i].start();
		}
	}

	// 获取下载的完成百分比
	public double getCompleteRate()
	{
		// 统计多条线程已经下载的总大小
		int sumSize = 0;
		for (int i = 0; i < threadNum; i++)
		{
			sumSize += threads[i].length;
		}
		// 返回已经完成的百分比
		return sumSize * 1.0 / fileSize;
	}

	private class DownThread extends Thread
	{
		// 当前线程的下载位置
		private int startPos;
		// 定义当前线程负责下载的文件大小
		private int currentPartSize;
		// 当前线程需要下载的文件块
		private RandomAccessFile currentPart;
		// 定义已经该线程已下载的字节数
		public int length;

		public DownThread(int startPos, int currentPartSize,
			RandomAccessFile currentPart)
		{
			this.startPos = startPos;
			this.currentPartSize = currentPartSize;
			this.currentPart = currentPart;
		}

		@Override
		public void run()
		{
			try
			{
				URL url = new URL(path);
				HttpURLConnection conn = (HttpURLConnection)url
					.openConnection();
				conn.setConnectTimeout(5 * 1000);
				conn.setRequestMethod("GET");
				conn.setRequestProperty(
					"Accept",
					"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
					+ "application/x-shockwave-flash, application/xaml+xml, "
					+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
					+ "application/x-ms-application, application/vnd.ms-excel, "
					+ "application/vnd.ms-powerpoint, application/msword, */*");
				conn.setRequestProperty("Accept-Language", "zh-CN");
				conn.setRequestProperty("Charset", "UTF-8");
				InputStream inStream = conn.getInputStream();
				// 跳过startPos个字节，表明该线程只下载自己负责哪部分文件。
				inStream.skip(this.startPos);
				byte[] buffer = new byte[1024];
				int hasRead = 0;
				// 读取网络数据，并写入本地文件
				while (length < currentPartSize
					&& (hasRead = inStream.read(buffer)) != -1)
				{
					currentPart.write(buffer, 0, hasRead);
					// 累计该线程下载的总大小
					length += hasRead;
				}
				currentPart.close();
				inStream.close();
			}
			catch (Exception e)
			{
				e.printStackTrace();
			}
		}
	}
}

public class MultiThreadDown
{
	public static void main(String[] args) throws Exception
	{
		// 初始化DownUtil对象
		final DownUtil downUtil = new DownUtil("http://www.crazyit.org/"
			+ "attachment.php?aid=MTY0NXxjNjBiYzNjN3wxMzE1NTQ2MjU5fGNhO"
			+ "DlKVmpXVmhpNGlkWmVzR2JZbnluZWpqSllOd3JzckdodXJOMUpOWWt0aTJz,"
			, "oracelsql.rar", 4);
		// 开始下载
		downUtil.download();
		new Thread()
		{
			public void run()
			{
				while(downUtil.getCompleteRate() < 1)
				{
					// 每隔0.1秒查询一次任务的完成进度，
					// GUI程序中可根据该进度来绘制进度条
					System.out.println("已完成：" 
						+ downUtil.getCompleteRate());
					try
					{
						Thread.sleep(1000);
					}
					catch (Exception ex){}
				}
			}
		}.start();
	}
}

ublic class GetPostTest
{
	/**
	 * 向指定URL发送GET方法的请求
	 * @param url 发送请求的URL
	 * @param param 请求参数，格式满足name1=value1&name2=value2的形式。
	 * @return URL所代表远程资源的响应
	 */
	public static String sendGet(String url , String param) 
	{
		String result = "";
		String urlName = url + "?" + param;
		try
		{
			URL realUrl = new URL(urlName);
			// 打开和URL之间的连接
			URLConnection conn = realUrl.openConnection();
			// 设置通用的请求属性
			conn.setRequestProperty("accept", "*/*"); 
			conn.setRequestProperty("connection", "Keep-Alive"); 
			conn.setRequestProperty("user-agent"
				, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); 
			// 建立实际的连接
			conn.connect(); 
			// 获取所有响应头字段
			Map<String, List<String>> map = conn.getHeaderFields();
			// 遍历所有的响应头字段
			for (String key : map.keySet())
			{
				System.out.println(key + "--->" + map.get(key));
			}
			try(
				// 定义BufferedReader输入流来读取URL的响应
				BufferedReader in = new BufferedReader(
					new InputStreamReader(conn.getInputStream() , "utf-8")))
			{
				String line;
				while ((line = in.readLine())!= null)
				{
					result += "\n" + line;
				}
			}
		}
		catch(Exception e)
		{
			System.out.println("发送GET请求出现异常！" + e);
			e.printStackTrace();
		}
		return result;
	}
	/**
	 * 向指定URL发送POST方法的请求
	 * @param url 发送请求的URL
	 * @param param 请求参数，格式应该满足name1=value1&name2=value2的形式。
	 * @return URL所代表远程资源的响应
	 */	
	public static String sendPost(String url , String param)
	{
		String result = "";
		try
		{
			URL realUrl = new URL(url);
			// 打开和URL之间的连接
			URLConnection conn = realUrl.openConnection();
			// 设置通用的请求属性
			conn.setRequestProperty("accept", "*/*"); 
			conn.setRequestProperty("connection", "Keep-Alive"); 
			conn.setRequestProperty("user-agent", 
			"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); 
			// 发送POST请求必须设置如下两行
			conn.setDoOutput(true);
			conn.setDoInput(true);
			try(
				// 获取URLConnection对象对应的输出流
				PrintWriter out = new PrintWriter(conn.getOutputStream()))
			{
				// 发送请求参数
				out.print(param);
				// flush输出流的缓冲
				out.flush();
			}
			try(
				// 定义BufferedReader输入流来读取URL的响应
				BufferedReader in = new BufferedReader(new InputStreamReader
					(conn.getInputStream() , "utf-8")))
			{
				String line;
				while ((line = in.readLine())!= null)
				{
					result += "\n" + line;
				}
			}
		}
		catch(Exception e)
		{
			System.out.println("发送POST请求出现异常！" + e);
			e.printStackTrace();
		}
		return result;
	}
	// 提供主方法，测试发送GET请求和POST请求
	public static void main(String args[])
	{
		// 发送GET请求
		String s = GetPostTest.sendGet("http://localhost:8888/abc/a.jsp"
			, null);
		System.out.println(s);
		// 发送POST请求
		String s1 = GetPostTest.sendPost("http://localhost:8888/abc/login.jsp"
			, "name=crazyit.org&pass=leegang");
		System.out.println(s1);
	}
}

public class Server
{
	public static void main(String[] args) 
		throws IOException
	{
		// 创建一个ServerSocket，用于监听客户端Socket的连接请求
		ServerSocket ss = new ServerSocket(30000);
		// 采用循环不断接受来自客户端的请求
		while (true)
		{
			// 每当接受到客户端Socket的请求，服务器端也对应产生一个Socket
			Socket s = ss.accept();
			// 将Socket对应的输出流包装成PrintStream
			PrintStream ps = new PrintStream(s.getOutputStream());
			// 进行普通IO操作
			ps.println("您好，您收到了服务器的新年祝福！");
			// 关闭输出流，关闭Socket
			ps.close();
			s.close();
		}
	}
}

public class Client
{
	public static void main(String[] args) 
		throws IOException
	{
		Socket socket = new Socket("127.0.0.1" , 30000);   //①
		// 将Socket对应的输入流包装成BufferedReader
		BufferedReader br = new BufferedReader(
		new InputStreamReader(socket.getInputStream()));
		// 进行普通IO操作
		String line = br.readLine();
		System.out.println("来自服务器的数据：" + line);
		// 关闭输入流、socket
		br.close();
		socket.close();
	}
}

try {
	Scanner scan = new Scanner(s.getInputStream());
	String line = scan.nextLine();
} ...

Socket s = new Socket();
s.connect(new InetAddress(host, port), 10000);

public class MyServer
{
	//定义保存所有Socket的ArrayList
	public static ArrayList<Socket> socketList
		= new ArrayList<>();
	public static void main(String[] args) 
		throws IOException
	{
		ServerSocket ss = new ServerSocket(30000);
		while(true)
		{
			// 此行代码会阻塞，将一直等待别人的连接
			Socket s = ss.accept();
			socketList.add(s);
			// 每当客户端连接后启动一条ServerThread线程为该客户端服务
			new Thread(new ServerThread(s)).start();
		}
	}
}

// 负责处理每个线程通信的线程类
public class ServerThread implements Runnable 
{
	// 定义当前线程所处理的Socket
	Socket s = null;
	// 该线程所处理的Socket所对应的输入流
	BufferedReader br = null;
	public ServerThread(Socket s)
	throws IOException
	{
		this.s = s;
		// 初始化该Socket对应的输入流
		br = new BufferedReader(new InputStreamReader(s.getInputStream()));
	}
	public void run()
	{
		try
		{
			String content = null;
			// 采用循环不断从Socket中读取客户端发送过来的数据
			while ((content = readFromClient()) != null)
			{
				// 遍历socketList中的每个Socket，
				// 将读到的内容向每个Socket发送一次
				for (Socket s : MyServer.socketList)
				{
					PrintStream ps = new PrintStream(s.getOutputStream());
					ps.println(content);
				}
			}
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
	}
	// 定义读取客户端数据的方法
	private String readFromClient()
	{
		try
		{
			return br.readLine();
		}
		// 如果捕捉到异常，表明该Socket对应的客户端已经关闭
		catch (IOException e)
		{
			// 删除该Socket。
			MyServer.socketList.remove(s);      // ①
		}
		return null;
	}
}

public class MyClient
{
	public static void main(String[] args)throws Exception 
	{
		Socket s = new Socket("127.0.0.1" , 30000);
		// 客户端启动ClientThread线程不断读取来自服务器的数据
		new Thread(new ClientThread(s)).start();   // ①
		// 获取该Socket对应的输出流
		PrintStream ps = new PrintStream(s.getOutputStream());
		String line = null;
		// 不断读取键盘输入
		BufferedReader br = new BufferedReader(
			new InputStreamReader(System.in));
		while ((line = br.readLine()) != null)
		{
			// 将用户的键盘输入内容写入Socket对应的输出流
			ps.println(line);
		}
	}
}

public class ClientThread implements Runnable
{
	// 该线程负责处理的Socket
	private Socket s;
	// 该线程所处理的Socket所对应的输入流
	BufferedReader br = null;
	public ClientThread(Socket s)
		throws IOException
	{
		this.s = s;
		br = new BufferedReader(
			new InputStreamReader(s.getInputStream()));
	}
	public void run()
	{
		try
		{
			String content = null;
			// 不断读取Socket输入流中的内容，并将这些内容打印输出
			while ((content = br.readLine()) != null)
			{
				System.out.println(content);
			}
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
}

public class Server
{
	public static void main(String[] args) 
		throws Exception
	{
		ServerSocket ss = new ServerSocket(30000);
		Socket socket = ss.accept();
		PrintStream ps = new PrintStream(socket.getOutputStream());
		ps.println("服务器的第一行数据");
		ps.println("服务器的第二行数据");
		//关闭socket的输出流，表明输出数据已经结束
		socket.shutdownOutput();
		//下面语句将输出false，表明socket还未关闭。
		System.out.println(socket.isClosed());
		Scanner scan = new Scanner(socket.getInputStream());
		while (scan.hasNextLine())
		{
			System.out.println(scan.nextLine());
		}
		scan.close();
		socket.close();
		ss.close();
	}
}

public class Client
{
	public static void main(String[] args)
		throws Exception
	{
		Socket s = new Socket("localhost" , 30000);
		Scanner scan = new Scanner(s.getInputStream());
		while (scan.hasNextLine())
		{
			System.out.println(scan.nextLine());
		}
		PrintStream ps = new PrintStream(s.getOutputStream());
		ps.println("客户端的第一行数据");
		ps.println("客户端的第二行数据");
		ps.close();
		scan.close();
		s.close();
	}
}

DatagramPacket packet = new DatagramPacket(buf, 256)
socket.receive(packet);  //等待数据报的到来

DatagramPacket packet = new DatagramPacket(buf, length, address, port);
socket.send(packet); //发送数据报

public class UdpServer
{
	public static final int PORT = 30000;
	// 定义每个数据报的最大大小为4K
	private static final int DATA_LEN = 4096;
	// 定义接收网络数据的字节数组
	byte[] inBuff = new byte[DATA_LEN];
	// 以指定字节数组创建准备接受数据的DatagramPacket对象
	private DatagramPacket inPacket = 
		new DatagramPacket(inBuff , inBuff.length);
	// 定义一个用于发送的DatagramPacket对象
	private DatagramPacket outPacket;
	// 定义一个字符串数组，服务器发送该数组的的元素
	String[] books = new String[]
	{
		"疯狂Java讲义",
		"轻量级Java EE企业应用实战",
		"疯狂Android讲义",
		"疯狂Ajax讲义"
	};
	public void init()throws IOException
	{
		try(
			// 创建DatagramSocket对象
			DatagramSocket socket = new DatagramSocket(PORT))
		{
			// 采用循环接受数据
			for (int i = 0; i < 1000 ; i++ )
			{
				// 读取Socket中的数据，读到的数据放入inPacket封装的数组里。
				socket.receive(inPacket);
				// 判断inPacket.getData()和inBuff是否是同一个数组
				System.out.println(inBuff == inPacket.getData());
				// 将接收到的内容转成字符串后输出
				System.out.println(new String(inBuff
					, 0 , inPacket.getLength()));
				// 从字符串数组中取出一个元素作为发送的数据
				byte[] sendData = books[i % 4].getBytes();
				// 以指定字节数组作为发送数据、以刚接受到的DatagramPacket的
				// 源SocketAddress作为目标SocketAddress创建DatagramPacket。
				outPacket = new DatagramPacket(sendData 
					, sendData.length , inPacket.getSocketAddress());
				// 发送数据
				socket.send(outPacket);
			}
		}
	}
	public static void main(String[] args)
		throws IOException
	{
		new UdpServer().init();
	}
}

public class UdpClient
{
	// 定义发送数据报的目的地
	public static final int DEST_PORT = 30000;
	public static final String DEST_IP = "127.0.0.1";
	// 定义每个数据报的最大大小为4K
	private static final int DATA_LEN = 4096;	
	// 定义接收网络数据的字节数组
	byte[] inBuff = new byte[DATA_LEN];
	// 以指定字节数组创建准备接受数据的DatagramPacket对象
	private DatagramPacket inPacket = 
		new DatagramPacket(inBuff , inBuff.length);
	// 定义一个用于发送的DatagramPacket对象
	private DatagramPacket outPacket = null;
	public void init()throws IOException
	{
		try(
			// 创建一个客户端DatagramSocket，使用随机端口
			DatagramSocket socket = new DatagramSocket())
		{
			// 初始化发送用的DatagramSocket，它包含一个长度为0的字节数组
			outPacket = new DatagramPacket(new byte[0] , 0
				, InetAddress.getByName(DEST_IP) , DEST_PORT);
			// 创建键盘输入流
			Scanner scan = new Scanner(System.in);
			// 不断读取键盘输入
			while(scan.hasNextLine())
			{
				// 将键盘输入的一行字符串转换字节数组
				byte[] buff = scan.nextLine().getBytes();
				// 设置发送用的DatagramPacket里的字节数据
				outPacket.setData(buff);
				// 发送数据报
				socket.send(outPacket);
				// 读取Socket中的数据，读到的数据放在inPacket所封装的字节数组里。
				socket.receive(inPacket);
				System.out.println(new String(inBuff , 0
					, inPacket.getLength()));
			}
		}
	}
	public static void main(String[] args) 
		throws IOException
	{
		new UdpClient().init();
	}
}

public class MulticastSocketTest implements Runnable
{
	// 使用常量作为本程序的多点广播IP地址
	private static final String BROADCAST_IP
		= "230.0.0.1";
	// 使用常量作为本程序的多点广播目的的端口
	public static final int BROADCAST_PORT = 30000;
	// 定义每个数据报的最大大小为4K
	private static final int DATA_LEN = 4096;
	//定义本程序的MulticastSocket实例
	private MulticastSocket socket = null;
	private InetAddress broadcastAddress = null;
	private Scanner scan = null;
	// 定义接收网络数据的字节数组
	byte[] inBuff = new byte[DATA_LEN];
	// 以指定字节数组创建准备接受数据的DatagramPacket对象
	private DatagramPacket inPacket
		= new DatagramPacket(inBuff , inBuff.length);
	// 定义一个用于发送的DatagramPacket对象
	private DatagramPacket outPacket = null;
	public void init()throws IOException
	{
		try(
			// 创建键盘输入流
			Scanner scan = new Scanner(System.in))
		{
			// 创建用于发送、接收数据的MulticastSocket对象
			// 由于该MulticastSocket对象需要接收数据，所以有指定端口
			socket = new MulticastSocket(BROADCAST_PORT);
			broadcastAddress = InetAddress.getByName(BROADCAST_IP);
			// 将该socket加入指定的多点广播地址
			socket.joinGroup(broadcastAddress);
			// 设置本MulticastSocket发送的数据报会被回送到自身
			socket.setLoopbackMode(false);
			// 初始化发送用的DatagramSocket，它包含一个长度为0的字节数组
			outPacket = new DatagramPacket(new byte[0] 
				, 0 , broadcastAddress , BROADCAST_PORT);
			// 启动以本实例的run()方法作为线程体的线程
			new Thread(this).start();
			// 不断读取键盘输入
			while(scan.hasNextLine())
			{
				// 将键盘输入的一行字符串转换字节数组
				byte[] buff = scan.nextLine().getBytes();
				// 设置发送用的DatagramPacket里的字节数据
				outPacket.setData(buff);
				// 发送数据报
				socket.send(outPacket);
			}
		}
		finally
		{
			socket.close();
		}
	}
	public void run()
	{
		try
		{
			while(true)
			{
				// 读取Socket中的数据，读到的数据放在inPacket所封装的字节数组里。
				socket.receive(inPacket);
				// 打印输出从socket中读取的内容
				System.out.println("聊天信息：" + new String(inBuff 
					, 0 , inPacket.getLength()));
			}
		}
		// 捕捉异常
		catch (IOException ex)
		{
			ex.printStackTrace();
			try
			{
				if (socket != null)
				{
					// 让该Socket离开该多点IP广播地址
					socket.leaveGroup(broadcastAddress);
					// 关闭该Socket对象
					socket.close();
				}
				System.exit(1);	
			}
			catch (IOException e)
			{
				e.printStackTrace();
			}
		}
	}
	public static void main(String[] args) 
		throws IOException
	{
		new MulticastSocketTest().init();
	}
}

try {
	//业务实现代码
} catch(Exception e) {
	//Exception处理代码
}

public class DivTest
{
	public static void main(String[] args) 
	{
		try
		{
			int a = Integer.parseInt(args[0]);
			int b = Integer.parseInt(args[1]);
			int c = a / b;
			System.out.println("您输入的两个数相除的结果是：" + c );
		}
		catch (IndexOutOfBoundsException ie)
		{
			System.out.println("数组越界：运行程序时输入的参数个数不够");
		}
		catch (NumberFormatException ne)
		{
			System.out.println("数字格式异常：程序只能接受整数参数");
		}
		catch (ArithmeticException ae)
		{
			System.out.println("算术异常");
		}
		catch (Exception e)
		{
			System.out.println("未知异常");
		}
	}
}

public class MultiExceptionTest
{
	public static void main(String[] args) 
	{
		try
		{
			int a = Integer.parseInt(args[0]);
			int b = Integer.parseInt(args[1]);
			int c = a / b;
			System.out.println("您输入的两个数相除的结果是：" + c );
		}
		catch (IndexOutOfBoundsException|NumberFormatException
			|ArithmeticException ie)
		{
			System.out.println("程序发生了数组越界、数字格式异常、算术异常之一");
			// 捕捉多异常时，异常变量默认有final修饰，
			// 所以下面代码有错：
			ie = new ArithmeticException("test");  //①
		}
		catch (Exception e)
		{
			System.out.println("未知异常");
			// 捕捉一个类型的异常时，异常变量没有final修饰
			// 所以下面代码完全正确。
			e = new RuntimeException("test");    //②
		}
	}
}

public class AccessExceptionMsg
{
	public static void main(String[] args) 
	{
		try
		{
			FileInputStream fis = new FileInputStream("a.txt");
		}
		catch (IOException ioe)
		{
			System.out.println(ioe.getMessage());
			ioe.printStackTrace();
		}
	}
}

public class FinallyTest
{
	public static void main(String[] args) 
	{
		FileInputStream fis = null;
		try
		{
			fis = new FileInputStream("a.txt");
		}
		catch (IOException ioe)
		{
			System.out.println(ioe.getMessage());
			//return语句强制方法返回
			return ;       //①
			//使用exit来退出虚拟机
			//System.exit(1);     //②
		}
		finally
		{
			//关闭磁盘文件，回收资源
			if (fis != null)
			{
				try
				{
					fis.close();
				}
				catch (IOException ioe)
				{
					ioe.printStackTrace();
				}
			}
			System.out.println("执行finally块里的资源回收!");
		}
	}
}

public class FinallyFlowTest
{
	public static void main(String[] args)
		throws Exception
	{
		boolean a = test();
		System.out.println(a);
	}
	public static boolean test()
	{
		try
		{
			// 因为finally块中包含了return语句
			// 所以下面的return语句失去作用
			return true;
		}
		finally
		{
			return false;
		}
	}
}

public class AutoCloseTest
{
	public static void main(String[] args) 
		throws IOException
	{
		try (
			// 声明、初始化两个可关闭的资源
			// try语句会自动关闭这两个资源。
			BufferedReader br = new BufferedReader(
				new FileReader("AutoCloseTest.java"));
			PrintStream ps = new PrintStream(new
				FileOutputStream("a.txt")))
		{
			// 使用两个资源
			System.out.println(br.readLine());
			ps.println("庄生晓梦迷蝴蝶");
		}
	}
}

public class ThrowsTest
{
	public static void main(String[] args)
		throws IOException
	{
		FileInputStream fis = new FileInputStream("a.txt");
	}
}

public class OverrideThrows
{
	public void test()throws IOException
	{
		FileInputStream fis = new FileInputStream("a.txt");
	}
}
class Sub extends OverrideThrows
{
	// 子类方法声明抛出了比父类方法更大的异常
	// 所以下面方法出错
	public void test()throws Exception
	{
	}
}

public class ThrowTest
{
	public static void main(String[] args) 
	{
		try
		{
			// 调用声明抛出Checked异常的方法，要么显式捕获该异常
			// 要么在main方法中再次声明抛出
			throwChecked(-3);
		}
		catch (Exception e)
		{
			System.out.println(e.getMessage());
		}
		// 调用声明抛出Runtime异常的方法既可以显式捕获该异常，
		// 也可不理会该异常
		throwRuntime(3);
	}
	public static void throwChecked(int a)throws Exception
	{
		if (a > 0)
		{
			//自行抛出Exception异常
			//该代码必须处于try块里，或处于带throws声明的方法中
			throw new Exception("a的值大于0，不符合要求");
		}
	}
	public static void throwRuntime(int a)
	{
		if (a > 0)
		{
			//自行抛出RuntimeException异常，既可以显式捕获该异常
			//也可完全不理会该异常，把该异常交给该方法调用者处理
			throw new RuntimeException("a的值大于0，不符合要求");
		}
	}
}

public class AuctionException extends Exception
{
	//无参数的构造器
	public AuctionException(){}       //①
	//带一个字符串参数的构造器
	public AuctionException(String msg)    //②
	{
		super(msg);
	}
}

public class AuctionTest
{
	private double initPrice = 30.0;
	// 因为该方法中显式抛出了AuctionException异常，
	// 所以此处需要声明抛出AuctionException异常
	public void bid(String bidPrice)
		throws AuctionException
	{
		double d = 0.0;
		try
		{
			d = Double.parseDouble(bidPrice);
		}
		catch (Exception e)
		{
			// 此处完成本方法中可以对异常执行的修复处理，
			// 此处仅仅是在控制台打印异常跟踪栈信息。
			e.printStackTrace();
			//再次抛出自定义异常
			throw new AuctionException("竞拍价必须是数值，"
				+ "不能包含其他字符！");
		}
		if (initPrice > d)
		{
			throw new AuctionException("竞拍价比起拍价低，"
				+ "不允许竞拍！");
		}
		initPrice = d;
	}
	public static void main(String[] args) 
	{
		AuctionTest at = new AuctionTest();
		try
		{
			at.bid("df");
		}
		catch (AuctionException ae)
		{
			// 再次捕捉到bid方法中的异常。并对该异常进行处理
			System.err.println(ae.getMessage());
		}
	}
}

public class SalException extends Exception
{
	public SalException(){}
	public SalException(String msg)
	{
		super(msg);
	}
	//创建一个可以接受Throwable参数的构造器
	public SalException(Throwable t)
	{
		super(t);
	}
}

class SelfException extends RuntimeException
{
	SelfException(){}
	SelfException(String msg)
	{
		super(msg);
	}
}
public class PrintStackTraceTest
{
	public static void main(String[] args)
	{
		firstMethod();
	}
	public static void firstMethod()
	{
		secondMethod();
	}
	public static void secondMethod()
	{
		thirdMethod();
	}
	public static void thirdMethod()
	{
		throw new SelfException("自定义异常信息");
	}
}

public class ThreadExceptionTest implements Runnable
{
	public void run()
	{
		firstMethod();
	}
	public void firstMethod()
	{
		secondMethod();
	}
	public void secondMethod()
	{
		int a = 5;
		int b = 0;
		int c = a / b;
	}
	public static void main(String[] args) 
	{
		new Thread(new ThreadExceptionTest()).start();
	}
}

package test.ant;
public class HelloWorld{
	public static void main(String[] args){
	System.out.println("Hello world1");
	}
};

public class FileTest
{
	public static void main(String[] args)
		throws IOException
	{
		// 以当前路径来创建一个File对象
		File file = new File("."); 
		// 直接获取文件名，输出一点
		System.out.println(file.getName());
		// 获取相对路径的父路径可能出错，下面代码输出null
		System.out.println(file.getParent());
		// 获取绝对路径
		System.out.println(file.getAbsoluteFile());
		// 获取上一级路径
		System.out.println(file.getAbsoluteFile().getParent());
		// 在当前路径下创建一个临时文件
		File tmpFile = File.createTempFile("aaa", ".txt", file);
		// 指定当JVM退出时删除该文件
		tmpFile.deleteOnExit();
		// 以系统当前时间作为新文件名来创建新文件
		File newFile = new File(System.currentTimeMillis() + "");
		System.out.println("newFile对象是否存在：" + newFile.exists());
		// 以指定newFile对象来创建一个文件
		newFile.createNewFile();
		// 以newFile对象来创建一个目录，因为newFile已经存在，
		// 所以下面方法返回false，即无法创建该目录
		newFile.mkdir();
		// 使用list()方法来列出当前路径下的所有文件和路径
		String[] fileList = file.list();
		System.out.println("====当前路径下所有文件和路径如下====");
		for (String fileName : fileList)
		{
			System.out.println(fileName);
		}
		// listRoots()静态方法列出所有的磁盘根路径。
		File[] roots = File.listRoots();
		System.out.println("====系统所有根路径如下====");
		for (File root : roots)
		{
			System.out.println(root);
		}
	}
}