Java IO体系之OutputStreamWriter

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介绍

• 字符输出流Writer 的实现类

继承关系图

样例

public static void main(String[] args) throws IOException{ 
   
    //创建字节输出流，绑定数据文件（没有则创建）
    FileOutputStream fos=new FileOutputStream("D:\\HELLO.txt");
    // 创建转换流对象，构造方法，绑定字节输出流
    OutputStreamWriter osw=new OutputStreamWriter(fos, "UTF-8");
    //转换流写数据（覆盖写）
    osw.append("春天到了").append("\r\n").append("春暖花开");
    osw.close();
    fos.close();
}

源码

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. */
    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. * * @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. * * @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. * * * @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();
    }
}

FileWriter源码

package java.io;

public class FileWriter extends OutputStreamWriter { 
   

    /** * Constructs a FileWriter object given a file name. * * @param fileName String The system-dependent filename. * @throws IOException if the named file exists but is a directory rather * than a regular file, does not exist but cannot be * created, or cannot be opened for any other reason */
    public FileWriter(String fileName) throws IOException { 
   
        super(new FileOutputStream(fileName));
    }

    /** * Constructs a FileWriter object given a file name with a boolean * indicating whether or not to append the data written. * * @param fileName String The system-dependent filename. * @param append boolean if <code>true</code>, then data will be written * to the end of the file rather than the beginning. * @throws IOException if the named file exists but is a directory rather * than a regular file, does not exist but cannot be * created, or cannot be opened for any other reason */
    public FileWriter(String fileName, boolean append) throws IOException { 
   
        super(new FileOutputStream(fileName, append));
    }

    /** * Constructs a FileWriter object given a File object. * * @param file a File object to write to. * @throws IOException if the file exists but is a directory rather than * a regular file, does not exist but cannot be created, * or cannot be opened for any other reason */
    public FileWriter(File file) throws IOException { 
   
        super(new FileOutputStream(file));
    }

    /** * Constructs a FileWriter object given a File object. If the second * argument is <code>true</code>, then bytes will be written to the end * of the file rather than the beginning. * * @param file a File object to write to * @param append if <code>true</code>, then bytes will be written * to the end of the file rather than the beginning * @throws IOException if the file exists but is a directory rather than * a regular file, does not exist but cannot be created, * or cannot be opened for any other reason * @since 1.4 */
    public FileWriter(File file, boolean append) throws IOException { 
   
        super(new FileOutputStream(file, append));
    }

    /** * Constructs a FileWriter object associated with a file descriptor. * * @param fd FileDescriptor object to write to. */
    public FileWriter(FileDescriptor fd) { 
   
        super(new FileOutputStream(fd));
    }

}