Java 7之传统I/O - InputStreamReader和OutputStreamWriter

// 将“字节输出流”转换成“字符输出流”  
public class OutputStreamWriter extends Writer {  
 
    private final StreamEncoder se;  // 字符到字节要进行解码
 
    // 根据out创建OutputStreamWriter，使用编码charsetName 
    public OutputStreamWriter(OutputStream out, String charsetName) throws UnsupportedEncodingException {  
        super(out);  
        if (charsetName == null)  
            throw new NullPointerException("charsetName");  
        se = StreamEncoder.forOutputStreamWriter(out, this, charsetName);  
    }  
 
    // 根据out创建OutputStreamWriter，使用默认的编码  
    public OutputStreamWriter(OutputStream out) {  
        super(out);  
        try {  
            se = StreamEncoder.forOutputStreamWriter(out, this, (String)null);  
        } catch (UnsupportedEncodingException e) {  
            throw new Error(e);  
        }  
    }  
 
    // 根据out创建OutputStreamWriter，使用编码cs  
    public OutputStreamWriter(OutputStream out, Charset cs) {  
        super(out);  
        if (cs == null)  
            throw new NullPointerException("charset");  
        se = StreamEncoder.forOutputStreamWriter(out, this, cs);  
    }  
 
    // 根据out创建OutputStreamWriter，使用编码器enc  
    public OutputStreamWriter(OutputStream out, CharsetEncoder enc) {  
        super(out);  
        if (enc == null)  
            throw new NullPointerException("charset encoder");  
        se = StreamEncoder.forOutputStreamWriter(out, this, enc);  
    }
 
    // 获取编码器enc  
    public String getEncoding() {  
        return se.getEncoding();  
    }  
 
    // 刷新缓冲区  
    void flushBuffer() throws IOException {  
        se.flushBuffer();  
    }  
 
    // 将单个字符写入到OutputStreamWriter中  
    public void write(int c) throws IOException {  
        se.write(c);  
    }  
 
    // 将字符数组cbuf从off开始的数据写入到OutputStreamWriter中，写入长度是len  
    public void write(char cbuf[], int off, int len) throws IOException {  
        se.write(cbuf, off, len);  
    }  
 
    // 将字符串str从off开始的数据写入到OutputStreamWriter中，写入长度是len  
    public void write(String str, int off, int len) throws IOException {  
        se.write(str, off, len);  
    } 
 
    // 刷新“输出流”  
    // 它与flushBuffer()的区别是：flushBuffer()只会刷新缓冲，而flush()是刷新流，flush()包括了flushBuffer  
    public void flush() throws IOException {  
        se.flush();  
    }  
 
    // 关闭“输出流”  
    public void close() throws IOException {  
        se.close();  
    }  
} 

    private static final String CharsetName = "utf-8"; // 使用支持中文编码的格式

    private static void testWrite() {
    	File file = new File("C:\\test.txt");
        try(OutputStreamWriter out1 = new OutputStreamWriter(new FileOutputStream(file), CharsetName);) {
            out1.write("积小流以成江海");             // 写入10个汉字
            out1.write("abcdefg\n");                  // 输出内容还有一个换行符"\n"
        } catch(IOException e) {
            e.printStackTrace();
        }
    }

// 将“字节输入流”转换成“字符输入流”  
public class InputStreamReader extends Reader {  
 
    private final StreamDecoder sd;  // 字节到字符要进行编码
 
    // 根据in创建InputStreamReader，使用默认的编码  
    public InputStreamReader(InputStream in) {  
        super(in);  
        try {  
            sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object  
        } catch (UnsupportedEncodingException e) {  
            throw new Error(e);  
        }  
    }  
 
    // 根据in创建InputStreamReader，使用编码charsetName(编码名)  
    public InputStreamReader(InputStream in, String charsetName)  
        throws UnsupportedEncodingException  
    {  
        super(in);  
        if (charsetName == null)  
            throw new NullPointerException("charsetName");  
        sd = StreamDecoder.forInputStreamReader(in, this, charsetName);  
    }  
 
    // 根据in创建InputStreamReader，使用编码cs  
    public InputStreamReader(InputStream in, Charset cs) {  
        super(in);  
        if (cs == null)  
            throw new NullPointerException("charset");  
        sd = StreamDecoder.forInputStreamReader(in, this, cs);  
    }  
 
    // 根据in创建InputStreamReader，使用解码器dec  
    public InputStreamReader(InputStream in, CharsetDecoder dec) {  
        super(in);  
        if (dec == null)  
            throw new NullPointerException("charset decoder");  
        sd = StreamDecoder.forInputStreamReader(in, this, dec);  
    }  
 
    // 获取解码器  
    public String getEncoding() {  
        return sd.getEncoding();  
    }  
 
    // 读取并返回一个字符  
    public int read() throws IOException {  
        return sd.read();  
    }  
 
    // 将InputStreamReader中的数据写入cbuf中，从cbuf的offset位置开始写入，写入长度是length  
    public int read(char cbuf[], int offset, int length) throws IOException {  
        return sd.read(cbuf, offset, length);  
    }  
 
    // 能否从InputStreamReader中读取数据  
    public boolean ready() throws IOException {  
        return sd.ready();  
    }  
 
    // 关闭InputStreamReader  
    public void close() throws IOException {  
        sd.close();  
    }  
} 

  private static void testRead() {
    	File file = new File("C:\\test.txt");
        try ( InputStreamReader isr = new InputStreamReader(new FileInputStream(file), CharsetName);){

            System.out.println("value1="+(char)isr.read());// 读取一个字节

            isr.skip(6);                  // 跳过4个字节进行读取
            System.out.println("value2="+(char)isr.read());

            char[] buf = new char[10];
            isr.read(buf, 0, buf.length); // 读取10个字符到buf数组中
            System.out.println("buf="+(new String(buf)));

        } catch(IOException e) {
            e.printStackTrace();
        }
    }