学步园

IO是JAVASE中非常重要的一块，是面向对象的完美体现，深入学习IO，你将可以领略到很多面向对象的思想。
在公司没活干，复习了一下IO，发现很多都忘记了，所以写的不好，只够初学用。我把我复习过程中写的代码贴出来，大家共同学习，并请多指教指教哈。顺便一起讨论IO
1、文件拷贝

try {
			File inputFile = new File(args[0]);
			if (!inputFile.exists()) {
				System.out.println("源文件不存在，程序终止");
				System.exit(1);
			}
			File outputFile = new File(args[1]);
			InputStream in = new FileInputStream(inputFile);
			OutputStream out = new FileOutputStream(outputFile);

			byte date[] = new byte[1024];
			int temp = 0;
			while ((temp = in.read(date)) != -1) {
				out.write(date);
			}

			in.close();
			out.close();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

2、java读文件:实现统计某一目录下每个文件中出现的字母个数、数字个数、空格个数及行数，除此之外没有其他字符

 String fileName = "D:/date.java.bak";
		// String fileName = "D:/test.qqq";
		String line;
		int i = 0, j = 0, f = 0, k = 0;
		try {
			BufferedReader in = new BufferedReader(new FileReader(fileName));
			line = in.readLine();
			while (line != null) {
				// System.out.println(line);
				char c[] = line.toCharArray();
				for (int i1 = 0; i1 < c.length; i1++) {
					// 如果是字母
					if (Character.isLetter(c[i1]))
						i++;
					// 如果是数字
					else if (Character.isDigit(c[i1]))
						j++;
					// 是空格
					else if (Character.isWhitespace(c[i1]))
						f++;
				}
				line = in.readLine();
				k++;
			}
			in.close();
			System.out
					.println("字母:" + i + ",数字:" + j + ",空格:" + f + ",行数:" + k);
		} catch (IOException e) {
			e.printStackTrace();
		}

3、 从文件（d:\test.txt）中查出字符串”aa”出现的次数

try {
			BufferedReader br = new BufferedReader(new FileReader(
					"D:\\test.txt"));
			StringBuilder sb = new StringBuilder();
			while (true) {
				String str = br.readLine();
				if (str == null)
					break;
				sb.append(str);
			}
			Pattern p = Pattern.compile("aa");
			Matcher m = p.matcher(sb);
			int count = 0;
			while (m.find()) {
				count++;
			}
			System.out.println("\"aa\"一共出现了" + count + "次");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

 4、 三种方法读取文件

 try {
			// 方法一
			BufferedReader br = new BufferedReader(new FileReader(new File(
					"D:\\1.xls")));
			// StringBuilder bd = new StringBuilder();
			StringBuffer bd = new StringBuffer();
			while (true) {
				String str = br.readLine();
				if (str == null) {
					break;
				}
				System.out.println(str);
				bd.append(str);
			}

			br.close();
			// System.out.println(bd.toString());

			// 方法二
			InputStream is = new FileInputStream(new File("d:\\1.xls"));
			byte b[] = new byte[Integer.parseInt(new File("d:\\1.xls").length()
					+ "")];
			is.read(b);
			System.out.write(b);
			System.out.println();
			is.close();

			// 方法三
			Reader r = new FileReader(new File("d:\\1.xls"));
			char c[] = new char[(int) new File("d:\\1.xls").length()];
			r.read(c);
			String str = new String(c);
			System.out.print(str);
			r.close();

		} catch (RuntimeException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

5、三种方法写文件

 try {
			PrintWriter pw = new PrintWriter(new FileWriter("d:\\1.txt"));
			BufferedWriter bw = new BufferedWriter(new FileWriter(new File(
					"d:\\1.txt")));
			OutputStream os = new FileOutputStream(new File("d:\\1.txt"));
			// 1
			os.write("ffff".getBytes());
			// 2
			// bw.write("ddddddddddddddddddddddddd");
			// 3
			// pw.print("你好sssssssssssss");

			bw.close();
			pw.close();
			os.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

6、读取文件，并把读取的每一行存入double型数组中

try {
			BufferedReader br = new BufferedReader(new FileReader(new File(
					"d:\\2.txt")));
			StringBuffer sb = new StringBuffer();
			while (true) {
				String str = br.readLine();
				if (str == null) {
					break;
				}
				sb.append(str + "、");
			}

			String str = sb.toString();
			String s[] = str.split("、");
			double d[] = new double[s.length];
			for (int i = 0; i < s.length; i++) {
				d[i] = Double.parseDouble(s[i]);
			}
			for (int i = 0; i < d.length; i++) {
				System.out.println(d[i]);
			}
			br.close();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}