【Java】字符流

/**====================================字符流=========================================
 * 天生具备了处理字符的能力，是一种可以直接读取字符的高级流
 =====================================================================================*/
public class CharIO {
	private static final long LEVEL = 20150701;//码讲版本
	//===============================标准字符流=======================================
	/*
	 * 字符输出流OutputStreamWriter
	 */
	//@Test
	public void testWriter() throws Exception{
		FileOutputStream out = new FileOutputStream("osw_utf8.txt");
		//OutputStreamWriter writer = new OutputStreamWriter(out);//使用默认字符集
		OutputStreamWriter writer = new OutputStreamWriter(out,"UTF-8");//自定义字符集
		String str = "测试用字符串";
		writer.write(str);//按字节写
		writer.write(str);
		writer.close();
	}
	/*
	 * 字符输入流InputStreamReader
	 */
	//@Test
	public void testReader()throws Exception{
		FileInputStream in = new FileInputStream("osw_utf8.txt");
		//InputStreamReader reader = new InputStreamReader(in);
		 InputStreamReader reader = new InputStreamReader(in,"UTF-8");//自定义字符集
		// 1、按字符读
		// int ch = -1;
		// while((ch = reader.read())!=-1){
		// System.out.print((char)ch);
		// }
		//
		//2、按字符数组读
		StringBuilder sb = new StringBuilder();
		char[] chs = new char[1024];
		int len = -1;
		while((len = reader.read(chs))!=-1){
			sb.append(chs, 0, len);
		}
		System.out.println(sb.toString());
		reader.close();
	}
	
	/**
	 * 转换文件编码 读取UTF-8编码文件，转为GBK，再存入
	 * @throws IOException 
	 */
	//@Test
	public void transCharsetDemo() throws IOException{
		transCharset("osw_utf8.txt","UTF-8","osw_GBK.txt","GBK");
	}
	private void transCharset (String srcName,String srcCharset,
			String targetName,String targetCharset) throws IOException{
		//TODO:只允许.txt类型文件
		FileInputStream in  = new FileInputStream(srcName);
		InputStreamReader reader = new InputStreamReader(in,srcCharset);
		FileOutputStream out = new FileOutputStream(targetName);
		OutputStreamWriter writer = new OutputStreamWriter(out,targetCharset);
		char[] chs = new char[1024];
		int len  = -1;
		while((len = reader.read(chs))!=-1){
			writer.write(chs, 0, len);
		}
		reader.close();
		writer.close();
	}
	/**===============================Buffered字符流=======================================
 	 * 以行为单位，快速读写字符串
	 * BufferedReader--PrintWriter(包装了BufferedWriter 提供自动行刷新)
	 =====================================================================================*/
	/*
	 * 使用PrintWriter写入数据
	 */
	//@Test
	public void testPrintWriter()throws Exception{
		
		PrintWriter writer1 = new PrintWriter("print.txt","UTF-8");
		writer1.println("测试PrintWriter");
		writer1.println("测试PrintWriter");
		//writer1.flush();//需要手动刷新才能print一行输出一行，即行刷新
		writer1.close();
	}
	/*
	 *  使用PrintWriter构造方法进行流嵌套
	 */
	//@Test
	public void testFlush()throws Exception{
		 //只嵌套字节流缺点：只能使用默认的字符集，不能指定字符集
		 //解决方法：转字节流为字符流嵌套给print即可
		FileOutputStream out = new FileOutputStream("flush.txt");
		 //嵌套流方式创建优点：可以在创建时，显式的声明需要行刷新，
		 //则每println(注意不是print方法)一次都会自动进行行刷新，即自动调用flush方法
		PrintWriter pw = new PrintWriter(out,true);//声明进行自动行刷新
		Scanner scan = new Scanner(System.in);
		String line = null;
		while(true){
			line = scan.nextLine();
			if("exit".equals(line)){
				System.out.println("退出！！");
				break;
			}
			pw.println(line);//具备了自动行刷新
		}
		pw.close();
	}
	/*
	 * BufferedReader读取数据
	 * 	读取将当前程序的源文件
	 */
	//@Test
	public void testBufferedReader()throws Exception{
		FileInputStream in = new FileInputStream("."+File.separator+"src"+
					File.separator+"api"+File.separator+"CharIO.java");
		BufferedReader reader = new BufferedReader(new InputStreamReader(in,"UTF-8"));
		String str = null;
		while((str = reader.readLine())!=null){//按行读取
			System.out.println(str);
		}
		reader.close();
	}
	/*
	 * 按行读取键盘输入内容
	 */
	@Test
	public void readUserLine() throws IOException{
		BufferedReader lineReader = new BufferedReader(new InputStreamReader(System.in));
		String str = null;
		while(true){
			str = lineReader.readLine();
			if("exit".equals(str)){
				System.out.println("退出！！");
				break;
			}
			System.out.println(str);
		}
		lineReader.close();
	}
}