Java经典实例

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");??
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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);??
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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,|",? true);??
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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??
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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();??
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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);??
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7. 结构化数据
Java代码?
1.? ? // 数组拷贝??
2.? ? System.arrayCopy(oldArray,newArray,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,TreeMap??
85.? ? containsValue(): 主 键(或给定值) - HashMap,TreeMap??
86.? ? indexOf(): 若 找到给定对象，返回其位置 - ArrayList,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??
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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.? ? }??
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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.? ? }??
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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,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,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);??
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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:testmytest.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:testmytest.txt");??
21.? ? f.renameTo(new File("c:testgoogle.txt"));??
22.? ? 把 mytest.txt修改成google.txt??
23.? ? ??
24.? ? // 删除文件??
25.? ? File f = new File("c:testmytest.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??
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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 rn");??
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 + "rn");??
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 + "rn");??
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 = "[email?protected]";??
3.? ? protected String msgSubject = "babytree";??
4.? ? protected String msgCc = "[email?protected]";??
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("[email?protected]"));??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. XMLSAX: 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 APICastor: 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:StudySourcejavacooksrc2xmlpeople.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,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:StudySourcejavacooksrc2xmlpeople.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. RMIJava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","22.0/7");??14.? ? System.out.println("Result type is " + r.getClass().getName());??15.? ? System.out.println("Result value is " + r);