Java IO體系之OutputStreamWriter

介紹

• 字符輸出流Writer 的實現類

繼承關係圖

樣例

    public static void main(String[] args)throws IOException {
        //創建字節輸出流，綁定數據文件（沒有則創建）
        FileOutputStream fos=new FileOutputStream("D:\\HELLO.txt");
        //創建轉換流對象，構造方法，綁定字節輸出流
        OutputStreamWriter osw=new OutputStreamWriter(fos,"UTF-8");
        //轉換流寫數據（覆蓋寫）
        osw.append("春天到了").append("\r\n").append("春暖花開");
        osw.close();
    }

源碼

package java.io;

import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import sun.nio.cs.StreamEncoder;

public class OutputStreamWriter extends Writer {

    private final StreamEncoder se;

    /**
     * Creates an OutputStreamWriter that uses the named charset.
     *
     * @param  out
     *         An OutputStream
     *
     * @param  charsetName
     *         The name of a supported
     *         {@link java.nio.charset.Charset charset}
     *
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     */
    public OutputStreamWriter(OutputStream out, String charsetName)
        throws UnsupportedEncodingException
    {
        super(out);
        if (charsetName == null)
            throw new NullPointerException("charsetName");
        se = StreamEncoder.forOutputStreamWriter(out, this, charsetName);
    }

    /**
     * Creates an OutputStreamWriter that uses the default character encoding.
     *
     * @param  out  An OutputStream
     */
    public OutputStreamWriter(OutputStream out) {
        super(out);
        try {
            se = StreamEncoder.forOutputStreamWriter(out, this, (String)null);
        } catch (UnsupportedEncodingException e) {
            throw new Error(e);
        }
    }

    /**
     * Creates an OutputStreamWriter that uses the given charset.
     *
     * @param  out
     *         An OutputStream
     *
     * @param  cs
     *         A charset
     *
     * @since 1.4
     * @spec JSR-51
     */
    public OutputStreamWriter(OutputStream out, Charset cs) {
        super(out);
        if (cs == null)
            throw new NullPointerException("charset");
        se = StreamEncoder.forOutputStreamWriter(out, this, cs);
    }

    /**
     * Creates an OutputStreamWriter that uses the given charset encoder.
     *
     * @param  out
     *         An OutputStream
     *
     * @param  enc
     *         A charset encoder
     *
     * @since 1.4
     * @spec JSR-51
     */
    public OutputStreamWriter(OutputStream out, CharsetEncoder enc) {
        super(out);
        if (enc == null)
            throw new NullPointerException("charset encoder");
        se = StreamEncoder.forOutputStreamWriter(out, this, enc);
    }

    /**
     * Returns the name of the character encoding being used by this stream.
     *
     * <p> If the encoding has an historical name then that name is returned;
     * otherwise the encoding's canonical name is returned.
     *
     * <p> If this instance was created with the {@link
     * #OutputStreamWriter(OutputStream, String)} constructor then the returned
     * name, being unique for the encoding, may differ from the name passed to
     * the constructor.  This method may return <tt>null</tt> if the stream has
     * been closed. </p>
     *
     * @return The historical name of this encoding, or possibly
     *         <code>null</code> if the stream has been closed
     *
     * @see java.nio.charset.Charset
     *
     * @revised 1.4
     * @spec JSR-51
     */
    public String getEncoding() {
        return se.getEncoding();
    }

    /**
     * Flushes the output buffer to the underlying byte stream, without flushing
     * the byte stream itself.  This method is non-private only so that it may
     * be invoked by PrintStream.
     */
    void flushBuffer() throws IOException {
        se.flushBuffer();
    }

    /**
     * Writes a single character.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(int c) throws IOException {
        se.write(c);
    }

    /**
     * Writes a portion of an array of characters.
     *
     * @param  cbuf  Buffer of characters
     * @param  off   Offset from which to start writing characters
     * @param  len   Number of characters to write
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(char cbuf[], int off, int len) throws IOException {
        se.write(cbuf, off, len);
    }

    /**
     * Writes a portion of a string.
     *
     * @param  str  A String
     * @param  off  Offset from which to start writing characters
     * @param  len  Number of characters to write
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(String str, int off, int len) throws IOException {
        se.write(str, off, len);
    }

    /**
     * Flushes the stream.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void flush() throws IOException {
        se.flush();
    }

    public void close() throws IOException {
        se.close();
    }
}