本文共 5241 字，大约阅读时间需要 17 分钟。

一、io的的介绍

1、网上盗图一张，主要的类结构

二、demo案例总结

1、Reader、Writer

     *  FileReader/FileWriter : 从文件读字符数据，写入字符数据到文件

@Test	public void test1() throws IOException {		// 1、FileReader/FileWriter		//Reader reader = new FileReader("");		//Writer writer = new FileWriter("");				// 2、CharArrayReader/Writer		//CharArrayReader charReader = new CharArrayReader("char array".toCharArray());		//CharArrayWriter charWriter = new CharArrayWriter(); 				// 3、BufferedReader/BufferedWriter		//BufferedReader bufferedReader = new BufferedReader(charReader);		//BufferedWriter wirter = new BufferedWriter(charWriter);				// 4 、基本操作范例		String source = "werrhewgergeorgergerg \r\nwer werwe ";		Reader input = new CharArrayReader(source.toCharArray());		CharArrayWriter output = new CharArrayWriter();		char[] buffer = new char[8061];        int n = 0;        while (-1 != (n = input.read(buffer))) {        	output.write(buffer, 0, n);        	//buffWrap.write(buffer, 0, n);        }        System.out.println(output.toCharArray());	}

 2、outputStream, InputStream 

     * FileInputStream/FileOutputStream : 从文件读取字节流，写入字节流到文件

@Test	public void test2() throws Exception {		// 1、FileInputStream/FileOutputStream		//InputStream in = new FileInputStream("file");		//OutputStream out = new FileOutputStream("file");				// 2、ByteArrayInputStream/output		//ByteArrayInputStream in = new ByteArrayInputStream("123".getBytes());		//ByteArrayOutputStream out = new ByteArrayOutputStream();				// 3、ObjectInputStream/ObjectInputStream 		     // 系列化		 ByteArrayOutputStream byteStream = new ByteArrayOutputStream(128);		 ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteStream);         objectOutputStream.writeObject(new Integer(1)); // 此对象必须是实现Serializable         objectOutputStream.flush();         byte[] result =  byteStream.toByteArray();             // 反系列化         ByteArrayInputStream intStream = new ByteArrayInputStream(result);         ObjectInputStream objectInputStream = new ObjectInputStream(intStream);         Object dis_result = objectInputStream.readObject();         System.out.println(dis_result); // 1	}

     3、OutputStreamWriter、InputStreamReader

@Test	public void test3() throws Exception {		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));		// OutputStreamWriter可以从字符串输出到字节流，并且可以指定编码。        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out,"UTF-8"));        String buf=null;		while ((buf = reader.readLine()) != null) {			if (buf.equals("exit"))				break;			writer.write(buf);			writer.newLine();			writer.flush();		}        reader.close();        writer.close();	}

4、字符打印流:PrintWriter

* 构造函数可以传递参数： File, String ,OutputStream, writer	 */	public void test4() throws IOException {		BufferedReader buff = new BufferedReader(new InputStreamReader(System.in)); //键盘录入		PrintWriter out1 = new PrintWriter(System.out); //标准输出 ,不自动刷新		//PrintWriter out2 = new PrintWriter(System.out, true); //true代表自动刷新 (只能用println,printf,print自动刷新)		String line = null;		while ((line = buff.readLine()) != null) {			if("ok".equals(line))				break;			out1.println(line.toUpperCase());		}		out1.close();		buff.close();	}

 5、File类的一些演示

// 1、基本操作		File f = new File(this.getClass().getClassLoader().getResource("").getPath()				+ File.separator + this.getClass().getName().replace(".", File.separator));		System.out.println(f.getParent()); // 本类文件的父级		if (!f.getParentFile().exists()) { // 创建父级目录 -- 文件父目录不存在不可创建文件			f.getParentFile().mkdirs();		}		File[] list = f.getParentFile().listFiles();		for (File file : list) {			System.out.println(file);		}		File f2 = new File(f.getParent()+File.separator+"abc.txt");		f2.createNewFile(); // 创建到了bin下了，在src下看不到的。				// 2、getAbsolutePath和getCanonicalPath区别		File file = new File("../src/java/a.text"); 		System.out.println(file.getPath()); 		System.out.println(file.getAbsolutePath());  // F:\java001\demo00_javase\..\src\java\a.text		System.out.println(file.getCanonicalPath()); // F:\java001\src\java\a.text

 6、获取包路径下的所有class文件

@Test	public void test6() {		String packageName = "com";		List
   
     list = findAllClassByPackage(packageName);		System.out.println(list);	}		/**	 * 获取包路径下所有的class	 */	public static List
    
      findAllClassByPackage(String pageAgeName) {		List
     
       result = new ArrayList<>();		String classPath = IO.class.getClassLoader().getResource("").getPath();		File file = new File(classPath + File.separator + pageAgeName.replace(".", File.separator));		if (!file.exists()) {			return result;		}		File[] files = file.listFiles();		for (int i = 0; i < files.length; i++) {			if (!files[i].isDirectory()) {				String className = files[i].getPath().replace(classPath.substring(1).replace("/", "\\"), "").replace("\\", ".")						.replace(".class", "");				result.add(className);			} else {				result.addAll(findAllClassByPackage(pageAgeName + "." + files[i].getName()));			}		}		return result;	}
     
    
   

转载地址：http://ieuni.baihongyu.com/