转换流

1. InputStreamReader

是Reader的子类，字符流对象，字节流向字符的桥梁。InputStreamReader有一个子类就是FileReader字节转成字符流。

构造方法：InputStreamReader(InputStream in)传递字节输入流，变成字符流

代码：

/* * 转换流，将字节转成字符流 * 实现读取一行的功能 * System.in * InputStreamReader--字节变字符，Reader的子类 * BufferedReader */import java.io.*;public class TranseDemo {public static void main(String[] args)throws IOException {//获取键盘输入的字节流InputStream in = System.in;//将键盘输入流，字节流in，转成字符流，//InputStreamReader构造方法中，传递字节输入流、InputStreamReader isr = new InputStreamReader(in);//可以使用字符流缓冲区读取一行BufferedReader bfr = new BufferedReader(isr);String line = null;while((line = bfr.readLine())!=null){if("over".equals(line))break;System.out.println(line.toUpperCase());}bfr.close();}}

2. 控制台输出  System.out

 System类的静态成员变量public static final PrintStream out;返回打印流对象，知道的是打印流对象也是字节输出流OutputStream的子类。

上面的程序，readLine()读取到的字符，不能直接写到字节输出流中，将字符流数据，转成字节流数据，写回控制台

3. OutputStreamWriter  是Writer的子类，字符流对象，字符流向字节的桥梁

OutputStreamWriter构造方法，传递的是字节输出流，System.out

代码：

import java.io.*;public class TranseDemo{public static void main(String[] args) throws IOException{//获取键盘输入的字节流InputStream in = System.in;//将键盘输入流，字节流in，转成字符流，InputStreamReader构造方法中，传递字节输入流、InputStreamReader isr = new InputStreamReader(in);//可以使用字符流缓冲区读取一行BufferedReader bfr = new BufferedReader(isr);//将读取到的readline()的数据输出到控制台，数据是一个字符流//输出数据的目的 System.out;//获得字节输出流对象OutputStream out = System.out;//将字符流转成字节流OutputStreamWriter osw = new OutputStreamWriter(out);//OutputStreamWriter是字符流，可以使用字符流缓冲区对象操作，//实现写换行BufferedWriter bfw = new BufferedWriter(osw);String line = null;while((line = bfr.readLine())!=null){if("over".equals(line))break;bfw.write(line.toUpperCase());bfw.newLine();bfw.flush();}bfw.close();bfr.close();}}

4.  转换流的案例

1）读取键盘输入，输入后的内容，转成大写，保存在一个记事本中

代码：

import java.io.*;public class TranseDemo {public static void main(String[] args)throws IOException {InputStream in = System.in;//键盘输入InputStreamReader isr = new InputStreamReader(in);BufferedReader bfr = new BufferedReader(isr);OutputStream out = new FileOutputStream("c:\\upper.txt");OutputStreamWriter osw = new OutputStreamWriter(out);BufferedWriter bfw = new BufferedWriter(osw);String line = null;while((line = bfr.readLine())!=null){if("over".equalsIgnoreCase(line))break;bfw.write(line.toUpperCase());bfw.newLine();bfw.flush();}bfw.close();bfr.close();}}

2）读取一个文本文件，转大写后，输出在控制台

代码：

import java.io.*;public class TranseDemo{public static void main(String[] args)throws IOException {InputStream in = new FileInputStream("src\\cn\\itcast\\iostream\\copytext3.java");InputStreamReader isr = new InputStreamReader(in);BufferedReader bfr = new BufferedReader(isr);OutputStream out = System.out;OutputStreamWriter osw = new OutputStreamWriter(out);BufferedWriter bfw = new BufferedWriter(osw);String line = null;while((line = bfr.readLine())!=null){if("over".equalsIgnoreCase(line))break;bfw.write(line.toUpperCase());bfw.newLine();bfw.flush();}bfw.close();bfr.close();}}

3）读取一个文本文件，转大写后，输出在另一个文件中

import java.io.*;public class TranseDemo{public static void main(String[] args)throws IOException {InputStream in = new FileInputStream("src\\cn\\itcast\\iostream\\copytext3.java");InputStreamReader isr = new InputStreamReader(in);BufferedReader bfr = new BufferedReader(isr);OutputStream out = new FileOutputStream("c:\\123.java");OutputStreamWriter osw = new OutputStreamWriter(out);BufferedWriter bfw = new BufferedWriter(osw);String line = null;while((line = bfr.readLine())!=null){if("over".equalsIgnoreCase(line))break;bfw.write(line.toUpperCase());bfw.newLine();bfw.flush();}bfw.close();bfr.close();}}