Java经典实例代码

Java经典实例(第二版)

1. 获取环境变量

Java代码

1. System.getenv("PATH");

2. System.getenv("JAVA_HOME");

2. 获取系统属性

Java代码

1. System.getProperty("pencil color"); // 得到属性值

2. java -Dpencil color=green

3. System.getProperty("java.specification.version"); // 得到Java版本号

4. Properties p = System.getProperties(); // 得到所有属性值

5. p.list(System.out);

3. StringTokenizer

Java代码

1. // 能够同时识别, 和 |

2. StringTokenizer st = new StringTokenizer("Hello, World|of|Java", ", |");

3. while (st.hasMoreElements()) {

4. st.nextToken();

5. }

6.

7. // 把分隔符视为token

8. StringTokenizer st = new StringTokenizer("Hello, World|of|Java", ", |", true);

4. StringBuffer(同步)和StringBuilder(非同步)

Java代码

1. StringBuilder sb = new StringBuilder();

2. sb.append("Hello");

3. sb.append("World");

4. sb.toString();

5. new StringBuffer(a).reverse(); // 反转字符串

5. 数字

Java代码

1. // 数字与对象之间互相转换 - Integer转int

2. Integer.intValue();

3.

4. // 浮点数的舍入

5. Math.round()

6.

7. // 数字格式化

8. NumberFormat

9.

10. // 整数 -> 二进制字符串

11. toBinaryString() 或valueOf()

12.

13. // 整数 -> 八进制字符串

14. toOctalString()

15.

16. // 整数 -> 十六进制字符串

17. toHexString()

18.

19. // 数字格式化为罗马数字

20. RomanNumberFormat()

21.

22. // 随机数

23. Random r = new Random();

24. r.nextDouble();

25. r.nextInt();

6. 日期和时间

Java代码

1. // 查看当前日期

2. Date today = new Date();

3. Calendar.getInstance().getTime();

4.

5. // 格式化默认区域日期输出

6. DateFormat df = DateFormat.getInstance();

7. df.format(today);

8.

9. // 格式化制定区域日期输出

10. DateFormat df_cn = DateFormat.getDateInstance(DateFormat.FULL, Locale.CHINA);

11. String now = df_cn.format(today);

12.

13. // 按要求格式打印日期

14. SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

15. sdf.format(today);

16.

17. // 设置具体日期

18. GregorianCalendar d1 = new GregorianCalendar(2009, 05, 06); // 6月6日

19. GregorianCalendar d2 = new GregorianCalendar(); // 今天

20. Calendar d3 = Calendar.getInstance(); // 今天

21. d1.getTime(); // Calendar或GregorianCalendar转成Date格式

22. d3.set(Calendar.YEAR, 1999);

23. d3.set(Calendar.MONTH, Calendar.APRIL);

24. d3.set(Calendar.DAY_OF_MONTH, 12);

25.

26. // 字符串转日期

27. SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

28. Date now = sdf.parse(String);

29.

30. // 日期加减

31. Date now = new Date();

32. long t = now.getTime();

33. t += 700*24*60*60*1000;

34. Date then = new Date(t);

35.

36. Calendar now = Calendar.getInstance();

37. now.add(Calendar.YEAR, -2);

38.

39. // 计算日期间隔(转换成long来计算)

40. today.getTime() - old.getTime();

41.

42. // 比较日期

43. Date 类型，就使用equals(), before(), after()来计算

44. long类型，就使用==, <, >来计算

45.

46. // 第几日

47. 使用 Calendar的get()方法

48. Calendar c = Calendar.getInstance();

49. c.get(Calendar.YEAR);

50.

51. // 记录耗时

52. long start = System.currentTimeMillis();

53. long end = System.currentTimeMillis();

54. long elapsed = end - start;

55. System.nanoTime(); //毫秒

56.

57. // 长整形转换成秒

58. Double.toString(t/1000D);

7. 结构化数据

Java代码

1. // 数组拷贝

2. System.arrayCopy(oldArray, 0, newArray, 0, oldArray.length);

3.

4. // ArrayList

5. add(Object o) // 在末尾添加给定元素

6. add(int i, Object o) // 在指定位置插入给定元素

7. clear() // 从集合中删除全部元素

8. Contains(Object o) // 如果Vector包含给定元素，返回真值

9. get(int i) // 返回 指定位置的对象句柄

10. indexOf(Object o) // 如果找到给定对象，则返回其索引值；否则，返回-1

11. remove(Object o) // 根据引用删除对象

12. remove(int i) // 根据 位置删除对象

13. toArray() // 返回包含集合对象的数组

14.

15. // Iterator

16. List list = new ArrayList();

17. Iterator it = list.iterator();

18. while (it.hasNext())

19. Object o = it.next();

20.

21. // 链表

22. LinkedList list = new LinkedList();

23. ListIterator it = list.listIterator();

24. while (it.hasNext())

25. Object o = it.next();

26.

27. // HashMap

28. HashMap<String, String> hm = new HashMap<String, String>();

29. hm.get(key); // 通过key得到value

30. hm.put("No1", "Hexinyu");

31. hm.put("No2", "Sean");

32. // 方法1: 获取全部键值

33. Iterator<String> it = hm.values().iterator();

34. while (it.hasNext()) {

35. String myKey = it.next();

36. String myValue = hm.get(myKey);

37. }

38. // 方法2: 获取全部键值

39. for (String key : hm.keySet()) {

40. String myKey = key;

41. String myValue = hm.get(myKey);

42. }

43.

44. // Preferences - 与系统相关的用户设置，类似名-值对

45. Preferences prefs = Preferences.userNodeForPackage(ArrayDemo.class);

46. String text = prefs.get("textFontName", "lucida-bright");

47. String display = prefs.get("displayFontName", "lucida-balckletter");

48. System.out.println(text);

49. System.out.println(display);

50. // 用户设置了新值，存储回去

51. prefs.put("textFontName", "new-bright");

52. prefs.put("displayFontName", "new-balckletter");

53.

54. // Properties - 类似名-值对，key和value之间，可以用"="，":"或空格分隔，用"#" 和"!"注释

55. InputStream in = MediationServer.class.getClassLoader().getResourceAsStream("msconfig.properties");

56. Properties prop = new Properties();

57. prop.load(in);

58. in.close();

59. prop.setProperty(key, value);

60. prop.getProperty(key);

61.

62. // 排序

63. 1. 数组：Arrays.sort(strings);

64. 2. List：Collections.sort(list);

65. 3. 自定义类：class SubComp implements Comparator

66. 然 后使用Arrays.sort(strings, new SubComp())

67.

68. // 两个接口

69. 1. java.lang.Comparable: 提供对象的自然排序，内置于类中

70. int compareTo(Object o);

71. boolean equals(Object o2);

72. 2. java.util.Comparator: 提供特定的比较方法

73. int compare(Object o1, Object o2)

74.

75. // 避免重复排序，可以使用TreeMap

76. TreeMap sorted = new TreeMap(unsortedHashMap);

77.

78. // 排除重复元素

79. Hashset hs - new HashSet();

80.

81. // 搜索对象

82. binarySearch(): 快 速查询 - Arrays, Collections

83. contains(): 线型搜 索 - ArrayList, HashSet, Hashtable, linkedList, Properties, Vector

84. containsKey(): 检 查集合对象是否包含给定 - HashMap, Hashtable, Properties, TreeMap

85. containsValue(): 主 键(或给定值) - HashMap, Hashtable, Properties, TreeMap

86. indexOf(): 若 找到给定对象，返回其位置 - ArrayList, linkedList, List, Stack, Vector

87. search(): 线 型搜素 - Stack

88.

89. // 集合转数组

90. toArray();

91.

92. // 集合总结

93. Collection: Set - HashSet, TreeSet

94. Collection: List - ArrayList, Vector, LinkedList

95. Map: HashMap, HashTable, TreeMap

8. 泛型与foreach

Java代码

1. // 泛型

2. List<String> myList = new ArrayList<String>();

3.

4. // foreach

5. for (String s : myList) {

6. System.out.println(s);

7. }

9. 面向对象

Java代码

1. // toString()格式化

2. public class ToStringWith {

3. int x, y;

4. public ToStringWith(int anX, int aY) {

5. x = anX;

6. y = aY;

7. }

8. public String toString() {

9. return "ToStringWith[" + x + "," + y + "]";

10. }

11. public static void main(String[] args) {

12. System.out.println(new ToStringWith(43, 78));

13. }

14. }

15.

16. // 覆盖equals方法

17. public boolean equals(Object o) {

18. if (o == this) // 优化

19. return true;

20. if (!(o instanceof EqualsDemo)) // 可投射到这个类

21. return false;

22. EqualsDemo other = (EqualsDemo)o; // 类型转换

23. if (int1 != other.int1) // 按字段比较

24. return false;

25. if (!obj1.equals(other.obj1))

26. return false;

27. return true;

28. }

29.

30. // 覆盖hashcode方法

31. private volatile int hashCode = 0; //延迟初始化

32. public int hashCode() {

33. if (hashCode == 0) {

34. int result = 17;

35. result = 37 * result + areaCode;

36. }

37. return hashCode;

38. }

39.

40. // Clone方法

41. 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

42. public class Clone1 implements Cloneable {

43. public Object clone() {

44. return super.clone();

45. }

46. }

47.

48. // Finalize方法

49. Object f = new Object() {

50. public void finalize() {

51. System.out.println("Running finalize()");

52. }

53. };

54. Runtime.getRuntime().addShutdownHook(new Thread() {

55. public void run() {

56. System.out.println("Running Shutdown Hook");

57. }

58. });

59. 在 调用System.exit(0);的时候，这两个方法将被执行

60.

61. // Singleton模式

62. // 实现1

63. public class MySingleton() {

64. public static final MySingleton INSTANCE = new MySingleton();

65. private MySingleton() {}

66. }

67. // 实现2

68. public class MySingleton() {

69. public static MySingleton instance = new MySingleton();

70. private MySingleton() {}

71. public static MySingleton getInstance() {

72. return instance;

73. }

74. }

75.

76. // 自定义异常

77. Exception: 编 译时检查

78. RuntimeException: 运行时检查

79. public class MyException extends RuntimeException {

80. public MyException() {

81. super();

82. }

83. public MyException(String msg) {

84. super(msg);

85. }

86. }

10. 输入和输出

Java代码

1. // Stream, Reader, Writer

2. Stream: 处 理字节流

3. Reader/Writer: 处理字符，通用Unicode

4.

5. // 从标准输入设备读数据

6. 1. 用System.in的BufferedInputStream()读取字节

7. int b = System.in.read();

8. System.out.println("Read data: " + (char)b); // 强 制转换为字符

9. 2. BufferedReader 读取文本

10. 如果从Stream转成Reader，使用 InputStreamReader类

11. BufferedReader is = new BufferedReader(new

12. InputStreamReader(System.in));

13. String inputLine;

14. while ((inputLine = is.readLine()) != null) {

15. System.out.println(inputLine);

16. int val = Integer.parseInt(inputLine); // 如果inputLine为整数

17. }

18. is.close();

19.

20. // 向标准输出设备写数据

21. 1. 用System.out的println()打印数据

22. 2. 用PrintWriter打印

23. PrintWriter pw = new PrintWriter(System.out);

24. pw.println("The answer is " + myAnswer + " at this time.");

25.

26. // Formatter类

27. 格 式化打印内容

28. Formatter fmtr = new Formatter();

29. fmtr.format("%1$04d - the year of %2$f", 1951, Math.PI);

30. 或 者System.out.printf();或者System.out.format();

31.

32. // 原始扫描

33. void doFile(Reader is) {

34. int c;

35. while ((c = is.read()) != -1) {

36. System.out.println((char)c);

37. }

38. }

39.

40. // Scanner扫描

41. Scanner 可以读取File, InputStream, String, Readable

42. try {

43. Scanner scan = new Scanner(new File("a.txt"));

44. while (scan.hasNext()) {

45. String s = scan.next();

46. }

47. } catch (FileNotFoundException e) {

48. e.printStackTrace();

49. }

50. }

51.

52. // 读取文件

53. BufferedReader is = new BufferedReader(new FileReader("myFile.txt"));

54. BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("bytes.bat"));

55. is.close();

56. bos.close();

57.

58. // 复制文件

59. BufferedIutputStream is = new BufferedIutputStream(new FileIutputStream("oldFile.txt"));

60. BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream("newFile.txt"));

61. int b;

62. while ((b = is.read()) != -1) {

63. os.write(b);

64. }

65. is.close();

66. os.close();

67.

68. // 文件读入字符串

69. StringBuffer sb = new StringBuffer();

70. char[] b = new char[8192];

71. int n;

72. // 读一个块，如果有字符，加入缓冲区

73. while ((n = is.read(b)) > 0) {

74. sb.append(b, 0, n);

75. }

76. return sb.toString();

77.

78. // 重定向标准流

79. String logfile = "error.log";

80. System.setErr(new PrintStream(new FileOutputStream(logfile)));

81.

82. // 读写不同字符集文本

83. BufferedReader chinese = new BufferedReader(new InputStreamReader(new FileInputStream("chinese.txt"), "ISO8859_1"));

84. PrintWriter standard = new PrintWriter(new OutputStreamWriter(new FileOutputStream("standard.txt"), "UTF-8"));

85.

86. // 读取二进制数据

87. DataOutputStream os = new DataOutputStream(new FileOutputStream("a.txt"));

88. os.writeInt(i);

89. os.writeDouble(d);

90. os.close();

91.

92. // 从指定位置读数据

93. RandomAccessFile raf = new RandomAccessFile(fileName, "r"); // r表示已 只读打开

94. raf.seek(15); // 从15开始读

95. raf.readInt();

96. raf.radLine();

97.

98. // 串行化对象

99. 对象串 行化，必须实现Serializable接口

100. // 保存 数据到磁盘

101. ObjectOutputStream os = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(FILENAME)));

102. os.writeObject(serialObject);

103. os.close();

104. // 读出数据

105. ObjectInputStream is = new ObjectInputStream(new FileInputStream(FILENAME));

106. is.readObject();

107. is.close();

108.

109. // 读写Jar或Zip文档

110. ZipFile zippy = new ZipFile("a.jar");

111. Enumeration all = zippy.entries(); // 枚举值列出所有文件清单

112. while (all.hasMoreElements()) {

113. ZipEntry entry = (ZipEntry)all.nextElement();

114. if (entry.isFile())

115. println("Directory: " + entry.getName());

116.

117. // 读写文件

118. FileOutputStream os = new FileOutputStream(entry.getName());

119. InputStream is = zippy.getInputStream(entry);

120. int n = 0;

121. byte[] b = new byte[8092];

122. while ((n = is.read(b)) > 0) {

123. os.write(b, 0, n);

124. is.close();

125. os.close();

126. }

127. }

128.

129. // 读写gzip文档

130. FileInputStream fin = new FileInputStream(FILENAME);

131. GZIPInputStream gzis = new GZIPInputStream(fin);

132. InputStreamReader xover = new InputStreamReader(gzis);

133. BufferedReader is = new BufferedReader(xover);

134. String line;

135. while ((line = is.readLine()) != null)

136. System.out.println("Read: " + line);

11. 目录和文件操作

Java代码

1. // 获取文件信息

2. exists(): 如 果文件存在，返回true

3. getCanonicalPath(): 获 取全名

4. getName(): 文件名

5. getParent(): 父 目录

6. canRead(): 如果文件可读，返回true

7. canWrite(): 如 果文件可写，返回true

8. lastModified(): 文 件更新时间

9. length(): 文件大小

10. isFile(): 如 果是文件，返回true

11. ifDirectory(): 如 果是目录，返回true

12. 要 调用文件的这些方法，必须

13. File f = new File(fileName);

14.

15. // 创建文件

16. File f = new File("c:\\test\\mytest.txt");

17. f.createNewFile(); // 创建mytest.txt文件到test目录下

18.

19. // 修改文件名

20. File f = new File("c:\\test\\mytest.txt");

21. f.renameTo(new File("c:\\test\\google.txt"));

22. 把 mytest.txt修改成google.txt

23.

24. // 删除文件

25. File f = new File("c:\\test\\mytest.txt");

26. f.delete();

27.

28. // 临时文件

29. File f = new File("C:\\test"); // 指定一个文件夹

30. // 在test文件夹中创建foo前缀，tmp后缀的临时文件

31. File tmp = File.createTempFile("foo", "tmp", f);

32. tmp.deleteOnExit(); // 在程序结束时删除该临时文件

33.

34. // 更改文件属性

35. setReadOnly(): 设 置为只读

36. setlastModified(): 设置最后更改时间

37.

38. // 列出当前文件夹的文件列表

39. String[] dir = new java.io.File(".").list();

40. java.util.Arrays.sort(dir);

41. for (int i = 0; i < dir.length; i++) {

42. System.out.println(dir[i]);

43. }

44.

45. // 过滤文件列表

46. class OnlyJava implements FilenameFilter {

47. public boolean accept(File dir, String s) {

48. if (s.endsWith(".java") || s.endsWith(".class") || s.endsWith(".jar"))

49. return true;

50. }

51. }

52.

53. // 获取根目录

54. File[] rootDir = File.listRoots();

55. for (int i = 0; i < rootDir.length; i++) {

56. System.out.println(rootDir[i]);

57. }

58.

59. // 创建新目录

60. new File("/home/ian/bin").mkdir(); // 如果"/home/ian"存在，则可以创建bin目录

61. new File("/home/ian/bin").mkdirs(); // 如果"/home/ian"不存在，会创建所有的目录

12. 国际化和本地化

Java代码

1. // I18N资源

2. ResourceBundle rb = ResourceBundle.getBundle("Menus");

3. String label = rb.getString("exit.label");

4. // ResourceBundle相当于名值对，获取Menus按钮的区域属性

5. Menus_cn.properties: 不 同区域的属性文件

6.

7. // 列出有效区域

8. Locale[] list = Locale.getAvailableLocales()；

9.

10. // 指定区域

11. Locale cnLocale = Locale.CHINA;

12.

13. // 设置默认区域

14. Locale.setDefault(Locale.CHINA);

15.

16. // 格式化消息

17. public class MessageFormatDemo {

18. static Object[] data = {

19. new java.util.Date(),

20. "myfile.txt",

21. "could nto be opened"

22. };

23. public static void main(String[] args) {

24. String result = MessageFormat.format("At {0,time} on {0,date}, {1} {2}.", data);

25. System.out.println(result);

26. }

27. }

28. 输 出: At 10:10:08 on 2009-6-18, myfile.txt could nto be opened.

29.

30. // 从资源文件中读消息

31. Widgets.properties 在com.sean.cook.chap11下

32. ResourceBundle rb = ResourceBundle.getBundle("com.sean.cook.chap11.Widgets");

33. String propt = rb.getString("filedialogs.cantopen.string");

34. String result = MessageFormat.format(rb.getString("filedialogs.cantopen.format"), data);

13. 网络客户端

Java代码

1. // 访问服务器

2. Socket socket = new Socket("127.0.0.1", 8080);

3. // todo something

4. socket.close();

5.

6. // 查找网络地址

7. InetAddress.getByName(hostName).getHostAddress()); // 根据主机名得到IP地址

8. InetAddress.getByName(ipAddr).getHostName()); // 根据IP地址得到主机名

9.

10. // 连接具体异常

11. UnknownHostException

12. NoRouteToHostException

13. ConnectException

14.

15. // Socket读写文本数据

16. BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

17. String remoteTime = in.readline();

18. PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

19. out.print("send message to client \r\n");

20. out.flush();

21.

22. // Socket读写二进制数据

23. DataInputStream in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));

24. long remoteTime = (long)(in.readUnsignedByte() << 24);

25. DataOutputStream out = new DataOutputStream(socket.getOutputStream(), true);

26.

27. // Socket读写串行化数据

28. ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));

29. Object o = in.readObject();

30. if (o instanceof Date) // 验证对象类型

31. ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream(), true);

32.

33. // UDP数据报

34. private final static int PACKET_SIZE = 1024;

35.

36. String host = "EV001B389673DE";

37. InetAddress serverAddr = InetAddress.getByName(host);

38. DatagramSocket socket = new DatagramSocket();

39. byte[] buffer = new byte[PACKET_SIZE]; // 分配数据缓冲空间

40. DatagramPacket packet = new DatagramPacket(buffer, PACKET_SIZE, serverAddr, 8080);

41. packet.setLength(PACKET_SIZE-1); // 设置数据长度

42. socket.send(packet);

43. socket.receive(packet); // 接收数据

14. 服务器端: Socket

Java代码

1. // 创建ServerSocket

2. ServerSocket serverSocket;

3. Socket clientSocket;

4.

5. serverSocket = new ServerSocket(9999);

6. while ((clientSocket = serverSocket.accept()) != null) {

7. System.out.println("Accept from client " + s.getInetAddress());

8. s.close();

9. }

10.

11. // 监听内部网

12. public static final short PORT = 9999;

13. public static final String INSIDE_HOST = "acmewidgets-inside"; // 网络接口名

14. public static final int BACKLOG = 10; // 待发数

15. serverSocket = new ServerSocket(PORT, BACKLOG, InetAddress.getByName(INSIDE_HOST));

16.

17. // 返回相应对象

18. ServerSocket serverSocket = new ServerSocket(9999);;

19. Socket clientSocket;

20. BufferedReader in = null;

21. PrintWriter out = null;

22. while (true) {

23. clientSocket = serverSocket.accept();

24. in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(), "8859_1"));

25. out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream(), "8859_1"), true);

26. String echoLine;

27. while ((echoLine = in.readLine()) != null) {

28. System.out.println("Read " + echoLine);

29. out.print(echoLine + "\r\n");

30. }

31. }

32. 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

33.

34. // 处理多客户端

35. 需要 把接收数据的处理放入多线程中

36. public class EchoServerThreaded {

37. public static final int ECHOPORT = 7;

38. public static final int NUM_THREADS = 4;

39.

40. public static void main(String[] av) {

41. new EchoServerThreaded(ECHOPORT, NUM_THREADS);

42. }

43.

44. public EchoServerThreaded2(int port, int numThreads) {

45. ServerSocket servSock;

46. Socket clientSocket;

47. try {

48. servSock = new ServerSocket(ECHOPORT);

49. } catch(IOException e) {

50. throw new RuntimeException("Could not create ServerSocket " + e);

51. }

52. for (int i = 0; i < numThreads; i++) {

53. new Handler(servSock, i).start();

54. }

55. }

56. }

57. class Handler extends Thread {

58. ServerSocket servSock;

59. int threadNumber;

60.

61. Handler(ServerSocket s, int i) {

62. super();

63. servSock = s;

64. threadNumber = i;

65. setName("Thread " + threadNumber);

66. }

67.

68. public void run() {

69. while (true) {

70. try {

71. System.out.println(getName() + " waiting");

72. Socket clientSocket;

73. synchronized (servSock) {

74. clientSocket = servSock.accept();

75. }

76. System.out.println(getName() + " starting, IP=" + clientSocket.getInetAddress());

77. BufferedReader is = new BufferedReader(new InputStreamReader(

78. clientSocket.getInputStream()));

79. PrintStream os = new PrintStream(clientSocket.getOutputStream(), true);

80. String line;

81. while ((line = is.readLine()) != null) {

82. os.print(line + "\r\n");

83. os.flush();

84. }

85. System.out.println(getName() + " ENDED ");

86. clientSocket.close();

87. } catch (IOException ex) {

88. System.out.println(getName() + ": IO Error on socket " + ex);

89. return;

90. }

91. }

92. }

93. }

94.

95. // 使用SSL和JSSE保护Web服务器

96. SSLServerSocketFactory ssf = (SSLServerSocketFactory)SSLServerSocketFactory.getDefault()；

97. ServerSocket serverSocket = ssf.createServerSocket(8080);

98.

99. // Log4j

100. Level 级别: DEBUG < INFO < WARN < ERROR < FATAL < OFF

101. Appender: 输 出信息

102. ConsoleAppender: 输出控制台 System.out

103.

104. // 找到网络接口

105. Enumeration list = NetworkInterface.getNetworkInterfaces();

106. while (list.hasMoreElements()) {

107. NetworkInterface iface = (NetworkInterface)list.nextElement();

108. System.out.println(iface.getDisplayName());

109. Enumeration addrs = iface.getInetAddresses();

110. while (addrs.hasMoreElements()) {

111. InetAddress addr = (InetAddress)addrs.nextElement();

112. System.out.println(addr);

113. }

114. }

15. Java Mail

Java代码

1. // 发送Mail

2. protected String msgRecIp = "hxydream@163.com";

3. protected String msgSubject = "babytree";

4. protected String msgCc = "nobody@erewhon.com";

5. protected String msgBody = "test body";

6. protected Session session;

7. protected Message msg;

8.

9. public void doSend() {

10. // 创建属性文件

11. Properties props = new Properties();

12. props.put("mail.smtp.host", "mailhost");

13. // 创建Session对象

14. session = Session.getDefaultInstance(props, null);

15. session.setDebug(true);

16. msg = new MimeMessage(session); // 创建邮件

17. msg. setFrom(new InternetAddress("nobody@host.domain"));

18. InternetAddress toAddr = new InternetAddress(msgRecIp);

19. msg.addRecipient(Message.RecipientType.TO, toAddr);

20. InternetAddress ccAddr = new InternetAddress(msgCc);

21. msg.addRecipient(Message.RecipientType.CC, ccAddr);

22. msg.setSubject(msgSubject);

23. msg.setText(msgBody);

24. Transport.send(msg);

25. }

26.

27. // 发送MIME邮件

28. Multipart mp = new MimeMultipart();

29. BodyPart textPart = new MimeBodyPart();

30. textPart.setText(message_body); // 设置类型"text/plain"

31. BodyPart pixPart = new MimeBodyPart();

32. pixPart.setContent(html_data, "text/html");

33. mp.addBodyPart(textPart);

34. mp.addBodyPart(pixPart);

35. mesg.setContent(mp);

36. Transport.send(mesg);

37.

38. // 读Mail

39. Store store = session.getStore(protocol);

40. store.connect(host, user, password);

41. Folder rf;

42. rf = store.getFolder(root);

43. rf = store.getDefaultFolder();

44. rf.open(Folder.READ_WRITE);

16. 数据库访问

Java代码

1. // JDO

2. Properties p = new Properties();

3. p.load(new FileInputStream("jdo.properties"));

4. PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory(p);

5. PersistenceManager pm = pmf.getPersistenceManager();

6. // 提交数据

7. pm.currentTransaction().begin();

8. if (o instanceof Collection) {

9. pm.makePersistentAll((Collection) o);

10. } else {

11. pm.makePersistent(o);

12. }

13. pm.currentTransaction().commit();

14. pm.close();

15. // 取出数据

16. Object[] data = new Object[3];

17. pm.retrieveAll(data);

18. for (int i = 0; i < data.length; i++) {

19. System.out.println(data[i]);

20. }

21. pm.close();

22.

23. // 数据操作

24. Class clz = Class.forName("oracle.jdbc.driver.OracleDriver");

25. String dbUrl = "jdbc:oracle:thin:@192.168.0.23:1521#:nms";

26. Connection conn = DriverManager.getConnection(dbUrl, "su", "1234");

27. Statement stmt = conn.createStatement();

28. ResultSet rs = stmt.executeQuery("select * from pmtable");

29. while (rs.next()) {

30. String name = rs.getString(1);

31. String otherName = rs.getString("name");

32. }

33.

34. // 使用PreparedStatement提高性能，除了查询，都使用executeUpdate执行操作

35. PreparedStatement pstmt = conn.prepareStatement("select * from pmtable where name = ?");

36. pstmt.setString(1, "sean");

37. ResultSet rs = pstmt.executeQuery();

38.

39. // 调用存储过程

40. CallableStatement cs = conn.prepareCall("{ call ListDefunctUsers }");

41. ResultSet rs = cs.executeQuery();

42.

43. // 显示数据库表信息

44. DatabaseMetaData meta = conn.getMetaData();

45. meta.getDatabaseProductName();

46. meta.getDatabaseProductVersion();

47. meta.getDefaultTransactionIsolation();

17. 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

1. // 从对象中生成XML

2. private final static String FILENAME = "serial.xml";

3. public static void main(String[] args) throws IOException {

4. String a = "hard work and best callback";

5. new SerialDemoXML().write(a);

6. new SerialDemoXML().dump();

7. }

8. public void write(Object obj) throws IOException {

9. XMLEncoder os = new XMLEncoder(new BufferedOutputStream(new FileOutputStream(FILENAME)));

10. os.writeObject(obj);

11. os.close();

12. }

13. public void dump() throws IOException {

14. XMLDecoder out = new XMLDecoder(new BufferedInputStream(new FileInputStream(FILENAME)));

15. System.out.println(out.readObject());

16. out.close();

17. }

18. serial.xml 格式内容如下:

19. <?xml version="1.0" encoding="UTF-8"?>

20. <java version="1.6.0_02" class="java.beans.XMLDecoder">

21. <string>hard work and best callback</string>

22. </java>

23. 控 制台输出

24. hard work and best callback

25.

26. // XSLT转换XML

27. XSLT 可以用来对输出格式进行各种控制

28. Transformer tx = TransformerFactory.newInstance().newTransformer(new StreamSource("people.xml"));

29. tx.transform(new StreamSource("people.xml"), new StreamResult("people.html"));

30.

31. // 用SAX解析XML - 主要用于查找关键元素，不用全文遍历

32. public SaxLister() throws SAXException, IOException {

33. XMLReader parser = XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");

34. parser.setContentHandler(new PeopleHandler());

35. parser.parse("C:\\StudySource\\javacooksrc2\\xml\\people.xml");

36. }

37. class PeopleHandler extends DefaultHandler {

38. boolean parent = false;

39. boolean kids = false;

40. public void startElement(String nsURI, String localName, String rawName, Attributes attr) throws SAXException {

41. System.out.println("startElement: " + localName + "," + rawName);

42. if (rawName.equalsIgnoreCase("name"))

43. parent = true;

44. if (rawName.equalsIgnoreCase("children"))

45. kids = true;

46. }

47. public void characters(char[] ch, int start, int length) {

48. if (parent) {

49. System.out.println("Parent: " + new String(ch, start, length));

50. parent = false;

51. } else if (kids) {

52. System.out.println("Children: " + new String(ch, start, length));

53. kids = false;

54. }

55. }

56. public PeopleHandler() throws SAXException {

57. super();

58. }

59. }

60.

61. // DOM解析XML - 遍历整个树

62. String uri = "file:" + new File("C:\\StudySource\\javacooksrc2\\xml\\people.xml").getAbsolutePath();

63. DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

64. DocumentBuilder builder = factory.newDocumentBuilder();

65. Document doc = builder.parse(uri);

66. NodeList nodes = doc.getChildNodes();

67. for (int i = 0; i < nodes.getLength(); i++) {

68. Node n = nodes.item(i);

69. switch (n.getNodeType()) {

70. case Node.ELEMENT_NODE:

71. // todo

72. break;

73. case Node.TEXT_NODE:

74. // todo

75. break;

76. }

77. }

78.

79. // 使用DTD或者XSD验证

80. 定 义好DTD或XSD文件

81. XmlDocument doc = XmlDocument.createXmlDocument(uri, true);

82.

83. // 用DOM生成XML

84. DocumentBuilderFactory fact = DocumentBuilderFactory.newInstance();

85. DocumentBuilder parser = fact.newDocumentBuilder();

86. Document doc = parser.newDocument();

87. Node root = doc.createElement("Poem");

88. doc.appendChild(root);

89. Node stanza = doc.createElement("Stanza");

90. root.appendChild(stanza);

91. Node line = doc.createElement("Line");

92. stanza.appendChild(line);

93. line.appendChild(doc.createTextNode("Once, upon a midnight dreary"));

94. line = doc.createElement("Line");

95. stanza.appendChild(line);

96. line.appendChild(doc.createTextNode("While I pondered, weak and weary"));

18. RMI

Java代码

1. a. 定义 客户端与服务器之间的通信接口

2. public interface RemoteDate extends Remote {

3. public Date getRemoteDate() throws RemoteException;

4. public final static String LOOKUPNAME = "RemoteDate";

5. }

6.

7. b. 编 写RMI服务器

8. public class RemoteDateImpl extends UnicastRemoteObject implements RemoteDate {

9. public RemoteDateImpl() throws RemoteException {

10. super();

11. }

12. public Date getRemoteDate() throws RemoteException {

13. return new Date();

14. }

15. }

16. RemoteDateImpl im = new RemoteDateImpl();

17. System.out.println("DateServer starting...");

18. Naming.rebind(RemoteDate.LOOKUPNAME, im);

19. System.out.println("DateServer ready.");

20.

21. c. 运 行rmic生成stub

22. javac RemoteDateImpl.java

23. rmic RemoteDateImpl

24.

25. d. 编 写客户端

26. netConn = (RemoteDate)Naming.lookup(RemoteDate.LOOKUPNAME);

27. Date today = netConn.getRemoteDate();

28. System.out.println(today.toString());

29.

30. e. 确 保RMI注册表运行

31. rmiregistry

32.

33. f. 启 动服务器

34. java RemoteDateImpl

35.

36. g. 运 行客户端

37. java DateClient

19. 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

20. Java线程

Java代码

1. // 停止线程 - 不要使用stop()方法

2. private boolean done = false;

3. public void run() {

4. while (!done) {

5. //todo

6. }

7. }

8. public void shutDown() {

9. done = true;

10. }

11. 可 以调用shutDown()方法来结束线程

12.

13. // 如果读取IO的时候出现堵塞，那么可以使用下面方法

14. public void shutDown() throws IOException {

15. if (io != null)

16. io.close();

17. }

18.

19. // 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

20. Thread t = new Thread() {

21. public void run() {

22. System.out.println("Reading");

23. try {

24. System.in.read();

25. } catch (IOException e) {

26. System.err.println(e);

27. }

28. System.out.println("Thread finished.");

29. }

30. };

31. System.out.println("Starting");

32. t.start();

33. System.out.println("Joining");

34. try {

35. t.join();

36. } catch (InterruptedException e) {

37. System.out.println("Who dares imterrupt my sleep?");

38. }

39. System.out.println("Main finished.");

40.

41. // 加锁保证同步

42. Lock lock = new ReentrantLock();

43. try {

44. lock.lock();

45. // todo

46. } finally {

47. lock.unlock();

48. }

49.

50. 线 程通信wait(), notify(), notifyAll()

51. 生产者-消费者模式

52. Executors

21. 内省或“命令类的类”

Java代码

1. // 反射

2. Class c = Class.forName("java.lang.String");

3. Constructor[] cons = c.getConstructors();

4. for (int i = 0; i < cons.length; i++) {

5. System.out.println(cons[i].toString());

6. }

7. Method[] meths = c.getMethods();

8. for (int i = 0; i < meths.length; i++) {

9. System.out.println(meths[i].toString());

10. }

11.

12. // 动态装载类

13. Class c = Class.forName("java.lang.String");

14. Object obj = c.newInstance();

15.

16. // 通过反射调用类的方法

17. class X {

18. public void master(String s) {

19. System.out.println("Working on \"" + s + "\"");

20. }

21. }

22. Class clx = X.class;

23. Class[] argTypes = {String.class};

24. Method worker = clx.getMethod("master", argTypes);

25. Object[] theData = {"Chocolate chips"};

26. worker.invoke(new X(), theData);

27. 输 出: Working on "Chocolate chips"

22. Java与其他语言的结合

Java代码

1. // 执行CMD命令，在Eclipse控制台输出

2. Process p = Runtime.getRuntime().exec("C:/StudySource/ver.cmd");

3. p.waitFor(); // 等待命令执行完

4. BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));

5. String s;

6. while ((s = br.readLine()) != null)

7. System.out.println(s);

8.

9. // 调用Jython - 计算22.0/7

10. BSFManager manager = new BSFManager();

11. String[] fntypes = {".py"};

12. manager.registerScriptingEngine("jython", "org.apache.bsf.engines.jython.JythonEngine", fntypes);

13. Object r = manager.eval("jython", "testString", 0, 0, "22.0/7");

14. System.out.println("Result type is " + r.getClass().getName());

15. System.out.println("Result value is " + r);