Java IO体系之OutputStreamWriter
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.
*
* 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 true, 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 true, 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 true, 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));
}
}