. 获取环境变量
Java代码
. System.getenv("PATH");
. System.getenv("JAVA_HOME");
. 获取系统属性
Java代码
. System.getProperty("pencil color"); // 得到属性值
. java -Dpencil color=green
. System.getProperty("java.specification.version"); // 得到Java版本号
. Properties p = System.getProperties(); // 得到所有属性值
. p.list(System.out);
. StringTokenizer
Java代码
. // 能够同时识别, 和 |
. StringTokenizer st = new StringTokenizer("Hello, World|of|Java", ", |");
. while (st.hasMoreElements()) {
. st.nextToken();
. }
.
. // 把分隔符视为token
. StringTokenizer st = new StringTokenizer("Hello, World|of|Java", ", |", true);
. StringBuffer(同步)和StringBuilder(非同步)
Java代码
. StringBuilder sb = new StringBuilder();
. sb.append("Hello");
. sb.append("World");
. sb.toString();
. new StringBuffer(a).reverse(); // 反转字符串
. 数字
Java代码
. // 数字与对象之间互相转换 - Integer转int
. Integer.intValue();
.
. // 浮点数的舍入
. Math.round()
.
. // 数字格式化
. NumberFormat
.
. // 整数 -> 二进制字符串
. toBinaryString() 或valueOf()
.
. // 整数 -> 八进制字符串
. toOctalString()
.
. // 整数 -> 十六进制字符串
. toHexString()
.
. // 数字格式化为罗马数字
. RomanNumberFormat()
.
. // 随机数
. Random r = new Random();
. r.nextDouble();
. r.nextInt();
. 日期和时间
Java代码
. // 查看当前日期
. Date today = new Date();
. Calendar.getInstance().getTime();
.
. // 格式化默认区域日期输出
. DateFormat df = DateFormat.getInstance();
. df.format(today);
.
. // 格式化制定区域日期输出
. DateFormat df_cn = DateFormat.getDateInstance(DateFormat.FULL, Locale.CHINA);
. String now = df_cn.format(today);
.
. // 按要求格式打印日期
. SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
. sdf.format(today);
.
. // 设置具体日期
. GregorianCalendar d1 = new GregorianCalendar(2009, 05, 06); // 6月6日
. GregorianCalendar d2 = new GregorianCalendar(); // 今天
. Calendar d3 = Calendar.getInstance(); // 今天
. d1.getTime(); // Calendar或GregorianCalendar转成Date格式
. d3.set(Calendar.YEAR, 1999);
. d3.set(Calendar.MONTH, Calendar.APRIL);
. d3.set(Calendar.DAY_OF_MONTH, 12);
.
. // 字符串转日期
. SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
. Date now = sdf.parse(String);
.
. // 日期加减
. Date now = new Date();
. long t = now.getTime();
. t += 700*24*60*60*1000;
. Date then = new Date(t);
.
. Calendar now = Calendar.getInstance();
. now.add(Calendar.YEAR, -2);
.
. // 计算日期间隔(转换成long来计算)
. today.getTime() - old.getTime();
.
. // 比较日期
. Date 类型，就使用equals(), before(), after()来计算
. long类型，就使用==, <, >来计算
.
. // 第几日
. 使用 Calendar的get()方法
. Calendar c = Calendar.getInstance();
. c.get(Calendar.YEAR);
.
. // 记录耗时
. long start = System.currentTimeMillis();
. long end = System.currentTimeMillis();
. long elapsed = end - start;
. System.nanoTime(); //毫秒
.
. // 长整形转换成秒
. Double.toString(t/1000D);
. 结构化数据
Java代码
. // 数组拷贝
. System.arrayCopy(oldArray, 0, newArray, 0, oldArray.length);
.
. // ArrayList
. add(Object o) // 在末尾添加给定元素
. add(int i, Object o) // 在指定位置插入给定元素
. clear() // 从集合中删除全部元素
. Contains(Object o) // 如果Vector包含给定元素，返回真值
. get(int i) // 返回 指定位置的对象句柄
. indexOf(Object o) // 如果找到给定对象，则返回其索引值；否则，返回-1
. remove(Object o) // 根据引用删除对象
. remove(int i) // 根据 位置删除对象
. toArray() // 返回包含集合对象的数组
.
. // Iterator
. List list = new ArrayList();
. Iterator it = list.iterator();
. while (it.hasNext())
. Object o = it.next();
.
. // 链表
. LinkedList list = new LinkedList();
. ListIterator it = list.listIterator();
. while (it.hasNext())
. Object o = it.next();
.
. // HashMap
. HashMap<String, String> hm = new HashMap<String, String>();
. hm.get(key); // 通过key得到value
. hm.put("No1", "Hexinyu");
. hm.put("No2", "Sean");
. // 方法1: 获取全部键值
. Iterator<String> it = hm.values().iterator();
. while (it.hasNext()) {
. String myKey = it.next();
. String myValue = hm.get(myKey);
. }
. // 方法2: 获取全部键值
. for (String key : hm.keySet()) {
. String myKey = key;
. String myValue = hm.get(myKey);
. }
.
. // Preferences - 与系统相关的用户设置，类似名-值对
. Preferences prefs = Preferences.userNodeForPackage(ArrayDemo.class);
. String text = prefs.get("textFontName", "lucida-bright");
. String display = prefs.get("displayFontName", "lucida-balckletter");
. System.out.println(text);
. System.out.println(display);
. // 用户设置了新值，存储回去
. prefs.put("textFontName", "new-bright");
. prefs.put("displayFontName", "new-balckletter");
.
. // Properties - 类似名-值对，key和value之间，可以用"="，":"或空格分隔，用"#" 和"!"注释
. InputStream in = MediationServer.class.getClassLoader().getResourceAsStream("msconfig.properties");
. Properties prop = new Properties();
. prop.load(in);
. in.close();
. prop.setProperty(key, value);
. prop.getProperty(key);
.
. // 排序
. 1. 数组：Arrays.sort(strings);
. 2. List：Collections.sort(list);
. 3. 自定义类：class SubComp implements Comparator
. 然 后使用Arrays.sort(strings, new SubComp())
.
. // 两个接口
. 1. java.lang.Comparable: 提供对象的自然排序，内置于类中
. int compareTo(Object o);
. boolean equals(Object o2);
. 2. java.util.Comparator: 提供特定的比较方法
. int compare(Object o1, Object o2)
.
. // 避免重复排序，可以使用TreeMap
. TreeMap sorted = new TreeMap(unsortedHashMap);
.
. // 排除重复元素
. Hashset hs - new HashSet();
.
. // 搜索对象
. binarySearch(): 快 速查询 - Arrays, Collections
. contains(): 线型搜 索 - ArrayList, HashSet, Hashtable, linkedList, Properties, Vector
. containsKey(): 检 查集合对象是否包含给定 - HashMap, Hashtable, Properties, TreeMap
. containsValue(): 主 键(或给定值) - HashMap, Hashtable, Properties, TreeMap
. indexOf(): 若 找到给定对象，返回其位置 - ArrayList, linkedList, List, Stack, Vector
. search(): 线 型搜素 - Stack
.
. // 集合转数组
. toArray();
.
. // 集合总结
. Collection: Set - HashSet, TreeSet
. Collection: List - ArrayList, Vector, LinkedList
. Map: HashMap, HashTable, TreeMap
. 泛型与foreach
Java代码
. // 泛型
. List<String> myList = new ArrayList<String>();
.
. // foreach
. for (String s : myList) {
. System.out.println(s);
. }
. 面向对象
Java代码
. // toString()格式化
. public class ToStringWith {
. int x, y;
. public ToStringWith(int anX, int aY) {
. x = anX;
. y = aY;
. }
. public String toString() {
. return "ToStringWith[" + x + "," + y + "]";
. }
. public static void main(String[] args) {
. System.out.println(new ToStringWith(43, 78));
. }
. }
.
. // 覆盖equals方法
. public boolean equals(Object o) {
. if (o == this) // 优化
. return true;
. if (!(o instanceof EqualsDemo)) // 可投射到这个类
. return false;
. EqualsDemo other = (EqualsDemo)o; // 类型转换
. if (int1 != other.int1) // 按字段比较
. return false;
. if (!obj1.equals(other.obj1))
. return false;
. return true;
. }
.
. // 覆盖hashcode方法
. private volatile int hashCode = 0; //延迟初始化
. public int hashCode() {
. if (hashCode == 0) {
. int result = 17;
. result = 37 * result + areaCode;
. }
. return hashCode;
. }
.
. // Clone方法
. 要 克隆对象，必须先做两步: 1. 覆盖对象的clone()方法; 2. 实现空的Cloneable接口
. public class Clone1 implements Cloneable {
. public Object clone() {
. return super.clone();
. }
. }
.
. // Finalize方法
. Object f = new Object() {
. public void finalize() {
. System.out.println("Running finalize()");
. }
. };
. Runtime.getRuntime().addShutdownHook(new Thread() {
. public void run() {
. System.out.println("Running Shutdown Hook");
. }
. });
. 在 调用System.exit(0);的时候，这两个方法将被执行
.
. // Singleton模式
. // 实现1
. public class MySingleton() {
. public static final MySingleton INSTANCE = new MySingleton();
. private MySingleton() {}
. }
. // 实现2
. public class MySingleton() {
. public static MySingleton instance = new MySingleton();
. private MySingleton() {}
. public static MySingleton getInstance() {
. return instance;
. }
. }
.
. // 自定义异常
. Exception: 编 译时检查
. RuntimeException: 运行时检查
. public class MyException extends RuntimeException {
. public MyException() {
. super();
. }
. public MyException(String msg) {
. super(msg);
. }
. }
. 输入和输出
Java代码
. // Stream, Reader, Writer
. Stream: 处 理字节流
. Reader/Writer: 处理字符，通用Unicode
.
. // 从标准输入设备读数据
. 1. 用System.in的BufferedInputStream()读取字节
. int b = System.in.read();
. System.out.println("Read data: " + (char)b); // 强 制转换为字符
. 2. BufferedReader 读取文本
. 如果从Stream转成Reader，使用 InputStreamReader类
. BufferedReader is = new BufferedReader(new
. InputStreamReader(System.in));
. String inputLine;
. while ((inputLine = is.readLine()) != null) {
. System.out.println(inputLine);
. int val = Integer.parseInt(inputLine); // 如果inputLine为整数
. }
. is.close();
.
. // 向标准输出设备写数据
. 1. 用System.out的println()打印数据
. 2. 用PrintWriter打印
. PrintWriter pw = new PrintWriter(System.out);
. pw.println("The answer is " + myAnswer + " at this time.");
.
. // Formatter类
. 格 式化打印内容
. Formatter fmtr = new Formatter();
. fmtr.format("%1$04d - the year of %2$f", 1951, Math.PI);
. 或 者System.out.printf();或者System.out.format();
.
. // 原始扫描
. void doFile(Reader is) {
. int c;
. while ((c = is.read()) != -1) {
. System.out.println((char)c);
. }
. }
.
. // Scanner扫描
. Scanner 可以读取File, InputStream, String, Readable
. try {
. Scanner scan = new Scanner(new File("a.txt"));
. while (scan.hasNext()) {
. String s = scan.next();
. }
. } catch (FileNotFoundException e) {
. e.printStackTrace();
. }
. }
.
. // 读取文件
. BufferedReader is = new BufferedReader(new FileReader("myFile.txt"));
. BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("bytes.bat"));
. is.close();
. bos.close();
.
. // 复制文件
. BufferedIutputStream is = new BufferedIutputStream(new FileIutputStream("oldFile.txt"));
. BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream("newFile.txt"));
. int b;
. while ((b = is.read()) != -1) {
. os.write(b);
. }
. is.close();
. os.close();
.
. // 文件读入字符串
. StringBuffer sb = new StringBuffer();
. char[] b = new char[8192];
. int n;
. // 读一个块，如果有字符，加入缓冲区
. while ((n = is.read(b)) > 0) {
. sb.append(b, 0, n);
. }
. return sb.toString();
.
. // 重定向标准流
. String logfile = "error.log";
. System.setErr(new PrintStream(new FileOutputStream(logfile)));
.
. // 读写不同字符集文本
. BufferedReader chinese = new BufferedReader(new InputStreamReader(new FileInputStream("chinese.txt"), "ISO8859_1"));
. PrintWriter standard = new PrintWriter(new OutputStreamWriter(new FileOutputStream("standard.txt"), "UTF-8"));
.
. // 读取二进制数据
. DataOutputStream os = new DataOutputStream(new FileOutputStream("a.txt"));
. os.writeInt(i);
. os.writeDouble(d);
. os.close();
.
. // 从指定位置读数据
. RandomAccessFile raf = new RandomAccessFile(fileName, "r"); // r表示已 只读打开
. raf.seek(15); // 从15开始读
. raf.readInt();
. raf.radLine();
.
. // 串行化对象
. 对象串 行化，必须实现Serializable接口
. // 保存 数据到磁盘
. ObjectOutputStream os = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(FILENAME)));
. os.writeObject(serialObject);
. os.close();
. // 读出数据
. ObjectInputStream is = new ObjectInputStream(new FileInputStream(FILENAME));
. is.readObject();
. is.close();
.
. // 读写Jar或Zip文档
. ZipFile zippy = new ZipFile("a.jar");
. Enumeration all = zippy.entries(); // 枚举值列出所有文件清单
. while (all.hasMoreElements()) {
. ZipEntry entry = (ZipEntry)all.nextElement();
. if (entry.isFile())
. println("Directory: " + entry.getName());
.
. // 读写文件
. FileOutputStream os = new FileOutputStream(entry.getName());
. InputStream is = zippy.getInputStream(entry);
. int n = 0;
. byte[] b = new byte[8092];
. while ((n = is.read(b)) > 0) {
. os.write(b, 0, n);
. is.close();
. os.close();
. }
. }
.
. // 读写gzip文档
. FileInputStream fin = new FileInputStream(FILENAME);
. GZIPInputStream gzis = new GZIPInputStream(fin);
. InputStreamReader xover = new InputStreamReader(gzis);
. BufferedReader is = new BufferedReader(xover);
. String line;
. while ((line = is.readLine()) != null)
. System.out.println("Read: " + line);
. 目录和文件操作
Java代码
. // 获取文件信息
. exists(): 如 果文件存在，返回true
. getCanonicalPath(): 获 取全名
. getName(): 文件名
. getParent(): 父 目录
. canRead(): 如果文件可读，返回true
. canWrite(): 如 果文件可写，返回true
. lastModified(): 文 件更新时间
. length(): 文件大小
. isFile(): 如 果是文件，返回true
. ifDirectory(): 如 果是目录，返回true
. 要 调用文件的这些方法，必须
. File f = new File(fileName);
.
. // 创建文件
. File f = new File("c:\\test\\mytest.txt");
. f.createNewFile(); // 创建mytest.txt文件到test目录下
.
. // 修改文件名
. File f = new File("c:\\test\\mytest.txt");
. f.renameTo(new File("c:\\test\\google.txt"));
. 把 mytest.txt修改成google.txt
.
. // 删除文件
. File f = new File("c:\\test\\mytest.txt");
. f.delete();
.
. // 临时文件
. File f = new File("C:\\test"); // 指定一个文件夹
. // 在test文件夹中创建foo前缀，tmp后缀的临时文件
. File tmp = File.createTempFile("foo", "tmp", f);
. tmp.deleteOnExit(); // 在程序结束时删除该临时文件
.
. // 更改文件属性
. setReadOnly(): 设 置为只读
. setlastModified(): 设置最后更改时间
.
. // 列出当前文件夹的文件列表
. String[] dir = new java.io.File(".").list();
. java.util.Arrays.sort(dir);
. for (int i = 0; i < dir.length; i++) {
. System.out.println(dir[i]);
. }
.
. // 过滤文件列表
. class OnlyJava implements FilenameFilter {
. public boolean accept(File dir, String s) {
. if (s.endsWith(".java") || s.endsWith(".class") || s.endsWith(".jar"))
. return true;
. }
. }
.
. // 获取根目录
. File[] rootDir = File.listRoots();
. for (int i = 0; i < rootDir.length; i++) {
. System.out.println(rootDir[i]);
. }
.
. // 创建新目录
. new File("/home/ian/bin").mkdir(); // 如果"/home/ian"存在，则可以创建bin目录
. new File("/home/ian/bin").mkdirs(); // 如果"/home/ian"不存在，会创建所有的目录
. 国际化和本地化
Java代码
. // I18N资源
. ResourceBundle rb = ResourceBundle.getBundle("Menus");
. String label = rb.getString("exit.label");
. // ResourceBundle相当于名值对，获取Menus按钮的区域属性
. Menus_cn.properties: 不 同区域的属性文件
.
. // 列出有效区域
. Locale[] list = Locale.getAvailableLocales()；
.
. // 指定区域
. Locale cnLocale = Locale.CHINA;
.
. // 设置默认区域
. Locale.setDefault(Locale.CHINA);
.
. // 格式化消息
. public class MessageFormatDemo {
. static Object[] data = {
. new java.util.Date(),
. "myfile.txt",
. "could nto be opened"
. };
. public static void main(String[] args) {
. String result = MessageFormat.format("At {0,time} on {0,date}, {1} {2}.", data);
. System.out.println(result);
. }
. }
. 输 出: At 10:10:08 on 2009-6-18, myfile.txt could nto be opened.
.
. // 从资源文件中读消息
. Widgets.properties 在com.sean.cook.chap11下
. ResourceBundle rb = ResourceBundle.getBundle("com.sean.cook.chap11.Widgets");
. String propt = rb.getString("filedialogs.cantopen.string");
. String result = MessageFormat.format(rb.getString("filedialogs.cantopen.format"), data);
. 网络客户端
Java代码
. // 访问服务器
. Socket socket = new Socket("127.0.0.1", 8080);
. // todo something
. socket.close();
.
. // 查找网络地址
. InetAddress.getByName(hostName).getHostAddress()); // 根据主机名得到IP地址
. InetAddress.getByName(ipAddr).getHostName()); // 根据IP地址得到主机名
.
. // 连接具体异常
. UnknownHostException
. NoRouteToHostException
. ConnectException
.
. // Socket读写文本数据
. BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
. String remoteTime = in.readline();
. PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
. out.print("send message to client \r\n");
. out.flush();
.
. // Socket读写二进制数据
. DataInputStream in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
. long remoteTime = (long)(in.readUnsignedByte() << 24);
. DataOutputStream out = new DataOutputStream(socket.getOutputStream(), true);
.
. // Socket读写串行化数据
. ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));
. Object o = in.readObject();
. if (o instanceof Date) // 验证对象类型
. ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream(), true);
.
. // UDP数据报
. private final static int PACKET_SIZE = 1024;
.
. String host = "EV001B389673DE";
. InetAddress serverAddr = InetAddress.getByName(host);
. DatagramSocket socket = new DatagramSocket();
. byte[] buffer = new byte[PACKET_SIZE]; // 分配数据缓冲空间
. DatagramPacket packet = new DatagramPacket(buffer, PACKET_SIZE, serverAddr, 8080);
. packet.setLength(PACKET_SIZE-1); // 设置数据长度
. socket.send(packet);
. socket.receive(packet); // 接收数据
. 服务器端: Socket
Java代码
. // 创建ServerSocket
. ServerSocket serverSocket;
. Socket clientSocket;
.
. serverSocket = new ServerSocket(9999);
. while ((clientSocket = serverSocket.accept()) != null) {
. System.out.println("Accept from client " + s.getInetAddress());
. s.close();
. }
.
. // 监听内部网
. public static final short PORT = 9999;
. public static final String INSIDE_HOST = "acmewidgets-inside"; // 网络接口名
. public static final int BACKLOG = 10; // 待发数
. serverSocket = new ServerSocket(PORT, BACKLOG, InetAddress.getByName(INSIDE_HOST));
.
. // 返回相应对象
. ServerSocket serverSocket = new ServerSocket(9999);;
. Socket clientSocket;
. BufferedReader in = null;
. PrintWriter out = null;
. while (true) {
. clientSocket = serverSocket.accept();
. in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(), "8859_1"));
. out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream(), "8859_1"), true);
. String echoLine;
. while ((echoLine = in.readLine()) != null) {
. System.out.println("Read " + echoLine);
. out.print(echoLine + "\r\n");
. }
. }
. 以 上例子返回字符串，如果返回二进制，则使用DataOutputStream；返回对象，使用ObjectOutputStream
.
. // 处理多客户端
. 需要 把接收数据的处理放入多线程中
. public class EchoServerThreaded {
. public static final int ECHOPORT = 7;
. public static final int NUM_THREADS = 4;
.
. public static void main(String[] av) {
. new EchoServerThreaded(ECHOPORT, NUM_THREADS);
. }
.
. public EchoServerThreaded2(int port, int numThreads) {
. ServerSocket servSock;
. Socket clientSocket;
. try {
. servSock = new ServerSocket(ECHOPORT);
. } catch(IOException e) {
. throw new RuntimeException("Could not create ServerSocket " + e);
. }
. for (int i = 0; i < numThreads; i++) {
. new Handler(servSock, i).start();
. }
. }
. }
. class Handler extends Thread {
. ServerSocket servSock;
. int threadNumber;
.
. Handler(ServerSocket s, int i) {
. super();
. servSock = s;
. threadNumber = i;
. setName("Thread " + threadNumber);
. }
.
. public void run() {
. while (true) {
. try {
. System.out.println(getName() + " waiting");
. Socket clientSocket;
. synchronized (servSock) {
. clientSocket = servSock.accept();
. }
. System.out.println(getName() + " starting, IP=" + clientSocket.getInetAddress());
. BufferedReader is = new BufferedReader(new InputStreamReader(
. clientSocket.getInputStream()));
. PrintStream os = new PrintStream(clientSocket.getOutputStream(), true);
. String line;
. while ((line = is.readLine()) != null) {
. os.print(line + "\r\n");
. os.flush();
. }
. System.out.println(getName() + " ENDED ");
. clientSocket.close();
. } catch (IOException ex) {
. System.out.println(getName() + ": IO Error on socket " + ex);
. return;
. }
. }
. }
. }
.
. // 使用SSL和JSSE保护Web服务器
. SSLServerSocketFactory ssf = (SSLServerSocketFactory)SSLServerSocketFactory.getDefault()；
. ServerSocket serverSocket = ssf.createServerSocket(8080);
.
. // Log4j
. Level 级别: DEBUG < INFO < WARN < ERROR < FATAL < OFF
. Appender: 输 出信息
. ConsoleAppender: 输出控制台 System.out
.
. // 找到网络接口
. Enumeration list = NetworkInterface.getNetworkInterfaces();
. while (list.hasMoreElements()) {
. NetworkInterface iface = (NetworkInterface)list.nextElement();
. System.out.println(iface.getDisplayName());
. Enumeration addrs = iface.getInetAddresses();
. while (addrs.hasMoreElements()) {
. InetAddress addr = (InetAddress)addrs.nextElement();
. System.out.println(addr);
. }
. }
. Java Mail
Java代码
. // 发送Mail
. protected String msgRecIp = "hxydream@163.com";
. protected String msgSubject = "babytree";
. protected String msgCc = "nobody@erewhon.com";
. protected String msgBody = "test body";
. protected Session session;
. protected Message msg;
.
. public void doSend() {
. // 创建属性文件
. Properties props = new Properties();
. props.put("mail.smtp.host", "mailhost");
. // 创建Session对象
. session = Session.getDefaultInstance(props, null);
. session.setDebug(true);
. msg = new MimeMessage(session); // 创建邮件
. msg. setFrom(new InternetAddress("nobody@host.domain"));
. InternetAddress toAddr = new InternetAddress(msgRecIp);
. msg.addRecipient(Message.RecipientType.TO, toAddr);
. InternetAddress ccAddr = new InternetAddress(msgCc);
. msg.addRecipient(Message.RecipientType.CC, ccAddr);
. msg.setSubject(msgSubject);
. msg.setText(msgBody);
. Transport.send(msg);
. }
.
. // 发送MIME邮件
. Multipart mp = new MimeMultipart();
. BodyPart textPart = new MimeBodyPart();
. textPart.setText(message_body); // 设置类型"text/plain"
. BodyPart pixPart = new MimeBodyPart();
. pixPart.setContent(html_data, "text/html");
. mp.addBodyPart(textPart);
. mp.addBodyPart(pixPart);
. mesg.setContent(mp);
. Transport.send(mesg);
.
. // 读Mail
. Store store = session.getStore(protocol);
. store.connect(host, user, password);
. Folder rf;
. rf = store.getFolder(root);
. rf = store.getDefaultFolder();
. rf.open(Folder.READ_WRITE);
. 数据库访问
Java代码
. // JDO
. Properties p = new Properties();
. p.load(new FileInputStream("jdo.properties"));
. PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory(p);
. PersistenceManager pm = pmf.getPersistenceManager();
. // 提交数据
. pm.currentTransaction().begin();
. if (o instanceof Collection) {
. pm.makePersistentAll((Collection) o);
. } else {
. pm.makePersistent(o);
. }
. pm.currentTransaction().commit();
. pm.close();
. // 取出数据
. Object[] data = new Object[3];
. pm.retrieveAll(data);
. for (int i = 0; i < data.length; i++) {
. System.out.println(data[i]);
. }
. pm.close();
.
. // 数据操作
. Class clz = Class.forName("oracle.jdbc.driver.OracleDriver");
. String dbUrl = "jdbc:oracle:thin:@192.168.0.23:1521#:nms";
. Connection conn = DriverManager.getConnection(dbUrl, "su", "1234");
. Statement stmt = conn.createStatement();
. ResultSet rs = stmt.executeQuery("select * from pmtable");
. while (rs.next()) {
. String name = rs.getString(1);
. String otherName = rs.getString("name");
. }
.
. // 使用PreparedStatement提高性能，除了查询，都使用executeUpdate执行操作
. PreparedStatement pstmt = conn.prepareStatement("select * from pmtable where name = ?");
. pstmt.setString(1, "sean");
. ResultSet rs = pstmt.executeQuery();
.
. // 调用存储过程
. CallableStatement cs = conn.prepareCall("{ call ListDefunctUsers }");
. ResultSet rs = cs.executeQuery();
.
. // 显示数据库表信息
. DatabaseMetaData meta = conn.getMetaData();
. meta.getDatabaseProductName();
. meta.getDatabaseProductVersion();
. meta.getDefaultTransactionIsolation();
. XML
SAX: 在读取文档提取相应的标记事件(元素起始、元素结束、文档起始)
DOM: 在内存中构造与文档中元素相应的树，可以遍历、搜索、修改
DTD: 验证文档是否正确
JAXP: 用于XML处理的Java API
Castor: 开源项目，用于Java对象与XML映射
Java代码
. // 从对象中生成XML
. private final static String FILENAME = "serial.xml";
. public static void main(String[] args) throws IOException {
. String a = "hard work and best callback";
. new SerialDemoXML().write(a);
. new SerialDemoXML().dump();
. }
. public void write(Object obj) throws IOException {
. XMLEncoder os = new XMLEncoder(new BufferedOutputStream(new FileOutputStream(FILENAME)));
. os.writeObject(obj);
. os.close();
. }
. public void dump() throws IOException {
. XMLDecoder out = new XMLDecoder(new BufferedInputStream(new FileInputStream(FILENAME)));
. System.out.println(out.readObject());
. out.close();
. }
. serial.xml 格式内容如下:
. <?xml version="1.0" encoding="UTF-8"?>
. <java version="1.6.0_02" class="java.beans.XMLDecoder">
. <string>hard work and best callback</string>
. </java>
. 控 制台输出
. hard work and best callback
.
. // XSLT转换XML
. XSLT 可以用来对输出格式进行各种控制
. Transformer tx = TransformerFactory.newInstance().newTransformer(new StreamSource("people.xml"));
. tx.transform(new StreamSource("people.xml"), new StreamResult("people.html"));
.
. // 用SAX解析XML - 主要用于查找关键元素，不用全文遍历
. public SaxLister() throws SAXException, IOException {
. XMLReader parser = XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");
. parser.setContentHandler(new PeopleHandler());
. parser.parse("C:\\StudySource\\javacooksrc2\\xml\\people.xml");
. }
. class PeopleHandler extends DefaultHandler {
. boolean parent = false;
. boolean kids = false;
. public void startElement(String nsURI, String localName, String rawName, Attributes attr) throws SAXException {
. System.out.println("startElement: " + localName + "," + rawName);
. if (rawName.equalsIgnoreCase("name"))
. parent = true;
. if (rawName.equalsIgnoreCase("children"))
. kids = true;
. }
. public void characters(char[] ch, int start, int length) {
. if (parent) {
. System.out.println("Parent: " + new String(ch, start, length));
. parent = false;
. } else if (kids) {
. System.out.println("Children: " + new String(ch, start, length));
. kids = false;
. }
. }
. public PeopleHandler() throws SAXException {
. super();
. }
. }
.
. // DOM解析XML - 遍历整个树
. String uri = "file:" + new File("C:\\StudySource\\javacooksrc2\\xml\\people.xml").getAbsolutePath();
. DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
. DocumentBuilder builder = factory.newDocumentBuilder();
. Document doc = builder.parse(uri);
. NodeList nodes = doc.getChildNodes();
. for (int i = 0; i < nodes.getLength(); i++) {
. Node n = nodes.item(i);
. switch (n.getNodeType()) {
. case Node.ELEMENT_NODE:
. // todo
. break;
. case Node.TEXT_NODE:
. // todo
. break;
. }
. }
.
. // 使用DTD或者XSD验证
. 定 义好DTD或XSD文件
. XmlDocument doc = XmlDocument.createXmlDocument(uri, true);
.
. // 用DOM生成XML
. DocumentBuilderFactory fact = DocumentBuilderFactory.newInstance();
. DocumentBuilder parser = fact.newDocumentBuilder();
. Document doc = parser.newDocument();
. Node root = doc.createElement("Poem");
. doc.appendChild(root);
. Node stanza = doc.createElement("Stanza");
. root.appendChild(stanza);
. Node line = doc.createElement("Line");
. stanza.appendChild(line);
. line.appendChild(doc.createTextNode("Once, upon a midnight dreary"));
. line = doc.createElement("Line");
. stanza.appendChild(line);
. line.appendChild(doc.createTextNode("While I pondered, weak and weary"));
. RMI
Java代码
. a. 定义 客户端与服务器之间的通信接口
. public interface RemoteDate extends Remote {
. public Date getRemoteDate() throws RemoteException;
. public final static String LOOKUPNAME = "RemoteDate";
. }
.
. b. 编 写RMI服务器
. public class RemoteDateImpl extends UnicastRemoteObject implements RemoteDate {
. public RemoteDateImpl() throws RemoteException {
. super();
. }
. public Date getRemoteDate() throws RemoteException {
. return new Date();
. }
. }
. RemoteDateImpl im = new RemoteDateImpl();
. System.out.println("DateServer starting...");
. Naming.rebind(RemoteDate.LOOKUPNAME, im);
. System.out.println("DateServer ready.");
.
. c. 运 行rmic生成stub
. javac RemoteDateImpl.java
. rmic RemoteDateImpl
.
. d. 编 写客户端
. netConn = (RemoteDate)Naming.lookup(RemoteDate.LOOKUPNAME);
. Date today = netConn.getRemoteDate();
. System.out.println(today.toString());
.
. e. 确 保RMI注册表运行
. rmiregistry
.
. f. 启 动服务器
. java RemoteDateImpl
.
. g. 运 行客户端
. java DateClient
. 包和包装机制
jar cvf /tmp/test.jar . // 当前目录压缩到test.jar中
jar xvf /tmp/test.jar // 把test.jar解压到当前目录
从指定class运行jar文件
a. Main-Class: HelloWord // 注意中间有一个空格
b. jar cvmf manifest.mf hello.jar HelloWorld.class
c. java -jar hello.jar
. Java线程
Java代码
. // 停止线程 - 不要使用stop()方法
. private boolean done = false;
. public void run() {
. while (!done) {
. //todo
. }
. }
. public void shutDown() {
. done = true;
. }
. 可 以调用shutDown()方法来结束线程
.
. // 如果读取IO的时候出现堵塞，那么可以使用下面方法
. public void shutDown() throws IOException {
. if (io != null)
. io.close();
. }
.
. // 启动一线程，等待控制台输入，使用join()方法来暂停当前线程，直到其他线程调用
. Thread t = new Thread() {
. public void run() {
. System.out.println("Reading");
. try {
. System.in.read();
. } catch (IOException e) {
. System.err.println(e);
. }
. System.out.println("Thread finished.");
. }
. };
. System.out.println("Starting");
. t.start();
. System.out.println("Joining");
. try {
. t.join();
. } catch (InterruptedException e) {
. System.out.println("Who dares imterrupt my sleep?");
. }
. System.out.println("Main finished.");
.
. // 加锁保证同步
. Lock lock = new ReentrantLock();
. try {
. lock.lock();
. // todo
. } finally {
. lock.unlock();
. }
.
. 线 程通信wait(), notify(), notifyAll()
. 生产者-消费者模式
. Executors
. 内省或“命令类的类”
Java代码
. // 反射
. Class c = Class.forName("java.lang.String");
. Constructor[] cons = c.getConstructors();
. for (int i = 0; i < cons.length; i++) {
. System.out.println(cons[i].toString());
. }
. Method[] meths = c.getMethods();
. for (int i = 0; i < meths.length; i++) {
. System.out.println(meths[i].toString());
. }
.
. // 动态装载类
. Class c = Class.forName("java.lang.String");
. Object obj = c.newInstance();
.
. // 通过反射调用类的方法
. class X {
. public void master(String s) {
. System.out.println("Working on \"" + s + "\"");
. }
. }
. Class clx = X.class;
. Class[] argTypes = {String.class};
. Method worker = clx.getMethod("master", argTypes);
. Object[] theData = {"Chocolate chips"};
. worker.invoke(new X(), theData);
. 输 出: Working on "Chocolate chips"
. Java与其他语言的结合
Java代码
. // 执行CMD命令，在Eclipse控制台输出
. Process p = Runtime.getRuntime().exec("C:/StudySource/ver.cmd");
. p.waitFor(); // 等待命令执行完
. BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
. String s;
. while ((s = br.readLine()) != null)
. System.out.println(s);
.
. // 调用Jython - 计算22.0/7
. BSFManager manager = new BSFManager();
. String[] fntypes = {".py"};
. manager.registerScriptingEngine("jython", "org.apache.bsf.engines.jython.JythonEngine", fntypes);
. Object r = manager.eval("jython", "testString", 0, 0, "22.0/7");
. System.out.println("Result type is " + r.getClass().getName());
. System.out.println("Result value is " + r);