/*
 * @(#)PrintWriter.java	1.37 04/07/16
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.io;

import java.util.Formatter;
import java.util.Locale;

/**
 * Print formatted representations of objects to a text-output stream.  This
 * class implements all of the <tt>print</tt> methods found in {@link
 * PrintStream}.  It does not contain methods for writing raw bytes, for which
 * a program should use unencoded byte streams.
 *
 * <p> Unlike the {@link PrintStream} class, if automatic flushing is enabled
 * it will be done only when one of the <tt>println</tt>, <tt>printf</tt>, or
 * <tt>format</tt> methods is invoked, rather than whenever a newline character
 * happens to be output.  These methods use the platform's own notion of line
 * separator rather than the newline character.
 *
 * <p> Methods in this class never throw I/O exceptions, although some of its
 * constructors may.  The client may inquire as to whether any errors have
 * occurred by invoking {@link #checkError checkError()}.
 *
 * @version 	1.37, 07/16/04
 * @author	Frank Yellin
 * @author	Mark Reinhold
 * @since	JDK1.1
 */

public class PrintWriter extends Writer {

    /**
     * The underlying character-output stream of this
     * <code>PrintWriter</code>.
     *
     * @since 1.2
     */
    protected Writer out;

    private boolean autoFlush = false;
    private boolean trouble = false;
    private Formatter formatter;

    /**
     * Line separator string.  This is the value of the line.separator
     * property at the moment that the stream was created.
     */
    private String lineSeparator;

    /**
     * Create a new PrintWriter, without automatic line flushing.
     *
     * @param  out        A character-output stream
     */
    public PrintWriter (Writer out) {
	this(out, false);
    }

    /**
     * Create a new PrintWriter.
     *
     * @param  out        A character-output stream
     * @param  autoFlush  A boolean; if true, the <tt>println</tt>,
     *                    <tt>printf</tt>, or <tt>format</tt> methods will
     *                    flush the output buffer
     */
    public PrintWriter(Writer out,
		       boolean autoFlush) {
	super(out);
	this.out = out;
	this.autoFlush = autoFlush;
	lineSeparator = (String) java.security.AccessController.doPrivileged(
               new sun.security.action.GetPropertyAction("line.separator"));
    }

    /**
     * Create a new PrintWriter, without automatic line flushing, from an
     * existing OutputStream.  This convenience constructor creates the
     * necessary intermediate OutputStreamWriter, which will convert characters
     * into bytes using the default character encoding.
     *
     * @param  out        An output stream
     *
     * @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
     */
    public PrintWriter(OutputStream out) {
	this(out, false);
    }

    /**
     * Create a new PrintWriter from an existing OutputStream.  This
     * convenience constructor creates the necessary intermediate
     * OutputStreamWriter, which will convert characters into bytes using the
     * default character encoding.
     *
     * @param  out        An output stream
     * @param  autoFlush  A boolean; if true, the <tt>println</tt>,
     *                    <tt>printf</tt>, or <tt>format</tt> methods will
     *                    flush the output buffer
     *
     * @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
     */
    public PrintWriter(OutputStream out, boolean autoFlush) {
	this(new BufferedWriter(new OutputStreamWriter(out)), autoFlush);
    }

    /**
     * Creates a new PrintWriter, without automatic line flushing, with the
     * specified file name.  This convenience constructor creates the necessary
     * intermediate {@link java.io.OutputStreamWriter OutputStreamWriter},
     * which will encode characters using the {@linkplain
     * java.nio.charset.Charset#defaultCharset default charset} for this
     * instance of the Java virtual machine.
     *
     * @param  fileName
     *         The name of the file to use as the destination of this writer.
     *         If the file exists then it will be truncated to zero size;
     *         otherwise, a new file will be created.  The output will be
     *         written to the file and is buffered.
     *
     * @throws  FileNotFoundException
     *          If the given string does not denote an existing, writable
     *          regular file and a new regular file of that name cannot be
     *          created, or if some other error occurs while opening or
     *          creating the file
     *
     * @throws  SecurityException
     *          If a security manager is present and {@link
     *          SecurityManager#checkWrite checkWrite(fileName)} denies write
     *          access to the file
     *
     * @since  1.5
     */
    public PrintWriter(String fileName) throws FileNotFoundException {
	this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileName))),
	     false);
    }

    /**
     * Creates a new PrintWriter, without automatic line flushing, with the
     * specified file name and charset.  This convenience constructor creates
     * the necessary intermediate {@link java.io.OutputStreamWriter
     * OutputStreamWriter}, which will encode characters using the provided
     * charset.
     *
     * @param  fileName
     *         The name of the file to use as the destination of this writer.
     *         If the file exists then it will be truncated to zero size;
     *         otherwise, a new file will be created.  The output will be
     *         written to the file and is buffered.
     *
     * @param  csn
     *         The name of a supported {@linkplain java.nio.charset.Charset
     *         charset}
     *
     * @throws  FileNotFoundException
     *          If the given string does not denote an existing, writable
     *          regular file and a new regular file of that name cannot be
     *          created, or if some other error occurs while opening or
     *          creating the file
     *
     * @throws  SecurityException
     *          If a security manager is present and {@link
     *          SecurityManager#checkWrite checkWrite(fileName)} denies write
     *          access to the file
     *
     * @throws  UnsupportedEncodingException
     *          If the named charset is not supported
     *
     * @since  1.5
     */
    public PrintWriter(String fileName, String csn)
	throws FileNotFoundException, UnsupportedEncodingException
    {
	this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileName), csn)),
	     false);
    }

    /**
     * Creates a new PrintWriter, without automatic line flushing, with the
     * specified file.  This convenience constructor creates the necessary
     * intermediate {@link java.io.OutputStreamWriter OutputStreamWriter},
     * which will encode characters using the {@linkplain
     * java.nio.charset.Charset#defaultCharset default charset} for this
     * instance of the Java virtual machine.
     *
     * @param  file
     *         The file to use as the destination of this writer.  If the file
     *         exists then it will be truncated to zero size; otherwise, a new
     *         file will be created.  The output will be written to the file
     *         and is buffered.
     *
     * @throws  FileNotFoundException
     *          If the given file object does not denote an existing, writable
     *          regular file and a new regular file of that name cannot be
     *          created, or if some other error occurs while opening or
     *          creating the file
     *
     * @throws  SecurityException
     *          If a security manager is present and {@link
     *          SecurityManager#checkWrite checkWrite(file.getPath())}
     *          denies write access to the file
     *
     * @since  1.5
     */
    public PrintWriter(File file) throws FileNotFoundException {
	this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file))),
	     false);
    }

    /**
     * Creates a new PrintWriter, without automatic line flushing, with the
     * specified file and charset.  This convenience constructor creates the
     * necessary intermediate {@link java.io.OutputStreamWriter
     * OutputStreamWriter}, which will encode characters using the provided
     * charset.
     *
     * @param  file
     *         The file to use as the destination of this writer.  If the file
     *         exists then it will be truncated to zero size; otherwise, a new
     *         file will be created.  The output will be written to the file
     *         and is buffered.
     *
     * @param  csn
     *         The name of a supported {@linkplain java.nio.charset.Charset
     *         charset}
     *
     * @throws  FileNotFoundException
     *          If the given file object does not denote an existing, writable
     *          regular file and a new regular file of that name cannot be
     *          created, or if some other error occurs while opening or
     *          creating the file
     *
     * @throws  SecurityException
     *          If a security manager is present and {@link
     *          SecurityManager#checkWrite checkWrite(file.getPath())}
     *          denies write access to the file
     *
     * @throws  UnsupportedEncodingException
     *          If the named charset is not supported
     *
     * @since  1.5
     */
    public PrintWriter(File file, String csn)
	throws FileNotFoundException, UnsupportedEncodingException
    {
	this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), csn)),
	     false);
    }

    /** Check to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
	if (out == null)
	    throw new IOException("Stream closed");
    }

    /**
     * Flush the stream.
     * @see #checkError()
     */
    public void flush() {
	try {
	    synchronized (lock) {
		ensureOpen();
		out.flush();
	    }
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Close the stream.
     * @see #checkError()
     */
    public void close() {
	try {
	    synchronized (lock) {
		if (out == null)
		    return;
		out.close();
		out = null;
	    }
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Flush the stream if it's not closed and check its error state.
     * Errors are cumulative; once the stream encounters an error, this
     * routine will return true on all successive calls.
     *
     * @return True if the print stream has encountered an error, either on the
     * underlying output stream or during a format conversion.
     */
    public boolean checkError() {
	if (out != null)
	    flush();
	return trouble;
    }

    /** Indicate that an error has occurred. */
    protected void setError() {
	trouble = true;
	try {
	    throw new IOException();
	} catch (IOException x) {
	}
    }


    /*
     * Exception-catching, synchronized output operations,
     * which also implement the write() methods of Writer
     */

    /**
     * Write a single character.
     * @param c int specifying a character to be written.
     */
    public void write(int c) {
	try {
	    synchronized (lock) {
		ensureOpen();
		out.write(c);
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Write A Portion of an array of characters.
     * @param buf Array of characters
     * @param off Offset from which to start writing characters
     * @param len Number of characters to write
     */
    public void write(char buf[], int off, int len) {
	try {
	    synchronized (lock) {
		ensureOpen();
		out.write(buf, off, len);
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Write an array of characters.  This method cannot be inherited from the
     * Writer class because it must suppress I/O exceptions.
     * @param buf Array of characters to be written
     */
    public void write(char buf[]) {
	write(buf, 0, buf.length);
    }

    /**
     * Write a portion of a string.
     * @param s A String
     * @param off Offset from which to start writing characters
     * @param len Number of characters to write
     */
    public void write(String s, int off, int len) {
	try {
	    synchronized (lock) {
		ensureOpen();
		out.write(s, off, len);
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Write a string.  This method cannot be inherited from the Writer class
     * because it must suppress I/O exceptions.
     * @param s String to be written
     */
    public void write(String s) {
	write(s, 0, s.length());
    }

    private void newLine() {
	try {
	    synchronized (lock) {
		ensureOpen();
		out.write(lineSeparator);
		if (autoFlush)
		    out.flush();
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }


    /* Methods that do not terminate lines */

    /**
     * Print a boolean value.  The string produced by <code>{@link
     * java.lang.String#valueOf(boolean)}</code> is translated into bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link
     * #write(int)}</code> method.
     *
     * @param      b   The <code>boolean</code> to be printed
     */
    public void print(boolean b) {
	write(b ? "true" : "false");
    }

    /**
     * Print a character.  The character is translated into one or more bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link
     * #write(int)}</code> method.
     *
     * @param      c   The <code>char</code> to be printed
     */
    public void print(char c) {
	write(c);
    }

    /**
     * Print an integer.  The string produced by <code>{@link
     * java.lang.String#valueOf(int)}</code> is translated into bytes according
     * to the platform's default character encoding, and these bytes are
     * written in exactly the manner of the <code>{@link #write(int)}</code>
     * method.
     *
     * @param      i   The <code>int</code> to be printed
     * @see        java.lang.Integer#toString(int)
     */
    public void print(int i) {
	write(String.valueOf(i));
    }

    /**
     * Print a long integer.  The string produced by <code>{@link
     * java.lang.String#valueOf(long)}</code> is translated into bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link #write(int)}</code>
     * method.
     *
     * @param      l   The <code>long</code> to be printed
     * @see        java.lang.Long#toString(long)
     */
    public void print(long l) {
	write(String.valueOf(l));
    }

    /**
     * Print a floating-point number.  The string produced by <code>{@link
     * java.lang.String#valueOf(float)}</code> is translated into bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link #write(int)}</code>
     * method.
     *
     * @param      f   The <code>float</code> to be printed
     * @see        java.lang.Float#toString(float)
     */
    public void print(float f) {
	write(String.valueOf(f));
    }

    /**
     * Print a double-precision floating-point number.  The string produced by
     * <code>{@link java.lang.String#valueOf(double)}</code> is translated into
     * bytes according to the platform's default character encoding, and these
     * bytes are written in exactly the manner of the <code>{@link
     * #write(int)}</code> method.
     *
     * @param      d   The <code>double</code> to be printed
     * @see        java.lang.Double#toString(double)
     */
    public void print(double d) {
	write(String.valueOf(d));
    }

    /**
     * Print an array of characters.  The characters are converted into bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link #write(int)}</code>
     * method.
     *
     * @param      s   The array of chars to be printed
     *
     * @throws  NullPointerException  If <code>s</code> is <code>null</code>
     */
    public void print(char s[]) {
	write(s);
    }

    /**
     * Print a string.  If the argument is <code>null</code> then the string
     * <code>"null"</code> is printed.  Otherwise, the string's characters are
     * converted into bytes according to the platform's default character
     * encoding, and these bytes are written in exactly the manner of the
     * <code>{@link #write(int)}</code> method.
     *
     * @param      s   The <code>String</code> to be printed
     */
    public void print(String s) {
	if (s == null) {
	    s = "null";
	}
	write(s);
    }

    /**
     * Print an object.  The string produced by the <code>{@link
     * java.lang.String#valueOf(Object)}</code> method is translated into bytes
     * according to the platform's default character encoding, and these bytes
     * are written in exactly the manner of the <code>{@link #write(int)}</code>
     * method.
     *
     * @param      obj   The <code>Object</code> to be printed
     * @see        java.lang.Object#toString()
     */
    public void print(Object obj) {
	write(String.valueOf(obj));
    }


    /* Methods that do terminate lines */

    /**
     * Terminate the current line by writing the line separator string.  The
     * line separator string is defined by the system property
     * <code>line.separator</code>, and is not necessarily a single newline
     * character (<code>'\n'</code>).
     */
    public void println() {
	newLine();
    }

    /**
     * Print a boolean value and then terminate the line.  This method behaves
     * as though it invokes <code>{@link #print(boolean)}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the <code>boolean</code> value to be printed
     */
    public void println(boolean x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print a character and then terminate the line.  This method behaves as
     * though it invokes <code>{@link #print(char)}</code> and then <code>{@link
     * #println()}</code>.
     *
     * @param x the <code>char</code> value to be printed
     */
    public void println(char x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print an integer and then terminate the line.  This method behaves as
     * though it invokes <code>{@link #print(int)}</code> and then <code>{@link
     * #println()}</code>.
     *
     * @param x the <code>int</code> value to be printed
     */
    public void println(int x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print a long integer and then terminate the line.  This method behaves
     * as though it invokes <code>{@link #print(long)}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the <code>long</code> value to be printed
     */
    public void println(long x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print a floating-point number and then terminate the line.  This method
     * behaves as though it invokes <code>{@link #print(float)}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the <code>float</code> value to be printed
     */
    public void println(float x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print a double-precision floating-point number and then terminate the
     * line.  This method behaves as though it invokes <code>{@link
     * #print(double)}</code> and then <code>{@link #println()}</code>.
     *
     * @param x the <code>double</code> value to be printed
     */
    public void println(double x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print an array of characters and then terminate the line.  This method
     * behaves as though it invokes <code>{@link #print(char[])}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the array of <code>char</code> values to be printed
     */
    public void println(char x[]) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print a String and then terminate the line.  This method behaves as
     * though it invokes <code>{@link #print(String)}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the <code>String</code> value to be printed
     */
    public void println(String x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * Print an Object and then terminate the line.  This method behaves as
     * though it invokes <code>{@link #print(Object)}</code> and then
     * <code>{@link #println()}</code>.
     *
     * @param x the <code>Object</code> value to be printed
     */
    public void println(Object x) {
	synchronized (lock) {
	    print(x);
	    println();
	}
    }

    /**
     * A convenience method to write a formatted string to this writer using
     * the specified format string and arguments.  If automatic flushing is
     * enabled, calls to this method will flush the output buffer.
     *
     * <p> An invocation of this method of the form <tt>out.printf(format,
     * args)</tt> behaves in exactly the same way as the invocation
     *
     * <pre>
     *     out.format(format, args) </pre>
     *
     * @param  format
     *         A format string as described in <a
     *         href="../util/Formatter.html#syntax">Format string syntax</a>.
     *
     * @param  args
     *         Arguments referenced by the format specifiers in the format
     *         string.  If there are more arguments than format specifiers, the
     *         extra arguments are ignored.  The number of arguments is
     *         variable and may be zero.  The maximum number of arguments is
     *         limited by the maximum dimension of a Java array as defined by
     *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
     *         Virtual Machine Specification</a>.  The behaviour on a
     *         <tt>null</tt> argument depends on the <a
     *         href="../util/Formatter.html#syntax">conversion</a>.
     *
     * @throws  IllegalFormatException
     *          If a format string contains an illegal syntax, a format
     *          specifier that is incompatible with the given arguments,
     *          insufficient arguments given the format string, or other
     *          illegal conditions.  For specification of all possible
     *          formatting errors, see the <a
     *          href="../util/Formatter.html#detail">Details</a> section of the
     *          formatter class specification.
     *
     * @throws  NullPointerException
     *          If the <tt>format</tt> is <tt>null</tt>
     *
     * @return  This writer
     *
     * @since  1.5
     */
    public PrintWriter printf(String format, Object ... args) {
	return format(format, args);
    }

    /**
     * A convenience method to write a formatted string to this writer using
     * the specified format string and arguments.  If automatic flushing is
     * enabled, calls to this method will flush the output buffer.
     *
     * <p> An invocation of this method of the form <tt>out.printf(l, format,
     * args)</tt> behaves in exactly the same way as the invocation
     *
     * <pre>
     *     out.format(l, format, args) </pre>
     *
     * @param  l
     *         The {@linkplain java.util.Locale locale} to apply during
     *         formatting.  If <tt>l</tt> is <tt>null</tt> then no localization
     *         is applied.
     *
     * @param  format
     *         A format string as described in <a
     *         href="../util/Formatter.html#syntax">Format string syntax</a>.
     *
     * @param  args
     *         Arguments referenced by the format specifiers in the format
     *         string.  If there are more arguments than format specifiers, the
     *         extra arguments are ignored.  The number of arguments is
     *         variable and may be zero.  The maximum number of arguments is
     *         limited by the maximum dimension of a Java array as defined by
     *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
     *         Virtual Machine Specification</a>.  The behaviour on a
     *         <tt>null</tt> argument depends on the <a
     *         href="../util/Formatter.html#syntax">conversion</a>.
     *
     * @throws  IllegalFormatException
     *          If a format string contains an illegal syntax, a format
     *          specifier that is incompatible with the given arguments,
     *          insufficient arguments given the format string, or other
     *          illegal conditions.  For specification of all possible
     *          formatting errors, see the <a
     *          href="../util/Formatter.html#detail">Details</a> section of the
     *          formatter class specification.
     *
     * @throws  NullPointerException
     *          If the <tt>format</tt> is <tt>null</tt>
     *
     * @return  This writer
     *
     * @since  1.5
     */
    public PrintWriter printf(Locale l, String format, Object ... args) {
	return format(l, format, args);
    }

    /**
     * Writes a formatted string to this writer using the specified format
     * string and arguments.  If automatic flushing is enabled, calls to this
     * method will flush the output buffer.
     *
     * <p> The locale always used is the one returned by {@link
     * java.util.Locale#getDefault() Locale.getDefault()}, regardless of any
     * previous invocations of other formatting methods on this object.
     *
     * @param  format
     *         A format string as described in <a
     *         href="../util/Formatter.html#syntax">Format string syntax</a>.
     *
     * @param  args
     *         Arguments referenced by the format specifiers in the format
     *         string.  If there are more arguments than format specifiers, the
     *         extra arguments are ignored.  The number of arguments is
     *         variable and may be zero.  The maximum number of arguments is
     *         limited by the maximum dimension of a Java array as defined by
     *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
     *         Virtual Machine Specification</a>.  The behaviour on a
     *         <tt>null</tt> argument depends on the <a
     *         href="../util/Formatter.html#syntax">conversion</a>.
     *
     * @throws  IllegalFormatException
     *          If a format string contains an illegal syntax, a format
     *          specifier that is incompatible with the given arguments,
     *          insufficient arguments given the format string, or other
     *          illegal conditions.  For specification of all possible
     *          formatting errors, see the <a
     *          href="../util/Formatter.html#detail">Details</a> section of the
     *          Formatter class specification.
     *
     * @throws  NullPointerException
     *          If the <tt>format</tt> is <tt>null</tt>
     *
     * @return  This writer
     *
     * @since  1.5
     */
    public PrintWriter format(String format, Object ... args) {
	try {
	    synchronized (lock) {
		ensureOpen();
		if ((formatter == null)
		    || (formatter.locale() != Locale.getDefault()))
		    formatter = new Formatter(this);
		formatter.format(Locale.getDefault(), format, args);
		if (autoFlush)
		    out.flush();
	    }
	} catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	} catch (IOException x) {
	    trouble = true;
	}
	return this;
    }

    /**
     * Writes a formatted string to this writer using the specified format
     * string and arguments.  If automatic flushing is enabled, calls to this
     * method will flush the output buffer.
     *
     * @param  l
     *         The {@linkplain java.util.Locale locale} to apply during
     *         formatting.  If <tt>l</tt> is <tt>null</tt> then no localization
     *         is applied.
     *
     * @param  format
     *         A format string as described in <a
     *         href="../util/Formatter.html#syntax">Format string syntax</a>.
     *
     * @param  args
     *         Arguments referenced by the format specifiers in the format
     *         string.  If there are more arguments than format specifiers, the
     *         extra arguments are ignored.  The number of arguments is
     *         variable and may be zero.  The maximum number of arguments is
     *         limited by the maximum dimension of a Java array as defined by
     *         the <a href="http://java.sun.com/docs/books/vmspec/">Java
     *         Virtual Machine Specification</a>.  The behaviour on a
     *         <tt>null</tt> argument depends on the <a
     *         href="../util/Formatter.html#syntax">conversion</a>.
     *
     * @throws  IllegalFormatException
     *          If a format string contains an illegal syntax, a format
     *          specifier that is incompatible with the given arguments,
     *          insufficient arguments given the format string, or other
     *          illegal conditions.  For specification of all possible
     *          formatting errors, see the <a
     *          href="../util/Formatter.html#detail">Details</a> section of the
     *          formatter class specification.
     *
     * @throws  NullPointerException
     *          If the <tt>format</tt> is <tt>null</tt>
     *
     * @return  This writer
     *
     * @since  1.5
     */
    public PrintWriter format(Locale l, String format, Object ... args) {
	try {
	    synchronized (lock) {
		ensureOpen();
		if ((formatter == null) || (formatter.locale() != l))
		    formatter = new Formatter(this, l);
		formatter.format(l, format, args);
		if (autoFlush)
		    out.flush();
	    }
	} catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	} catch (IOException x) {
	    trouble = true;
	}
	return this;
    }

    /**
     * Appends the specified character sequence to this writer.
     *
     * <p> An invocation of this method of the form <tt>out.append(csq)</tt>
     * behaves in exactly the same way as the invocation
     *
     * <pre>
     *     out.write(csq.toString()) </pre>
     *
     * <p> Depending on the specification of <tt>toString</tt> for the
     * character sequence <tt>csq</tt>, the entire sequence may not be
     * appended. For instance, invoking the <tt>toString</tt> method of a
     * character buffer will return a subsequence whose content depends upon
     * the buffer's position and limit.
     *
     * @param  csq
     *         The character sequence to append.  If <tt>csq</tt> is
     *         <tt>null</tt>, then the four characters <tt>"null"</tt> are
     *         appended to this writer.
     *
     * @return  This writer
     *
     * @since  1.5
     */
    public PrintWriter append(CharSequence csq) {
	if (csq == null)
	    write("null");
	else
	    write(csq.toString());
    	return this;
    }

    /**
     * Appends a subsequence of the specified character sequence to this writer.
     *
     * <p> An invocation of this method of the form <tt>out.append(csq, start,
     * end)</tt> when <tt>csq</tt> is not <tt>null</tt>, behaves in
     * exactly the same way as the invocation
     *
     * <pre>
     *     out.write(csq.subSequence(start, end).toString()) </pre>
     *
     * @param  csq
     *         The character sequence from which a subsequence will be
     *         appended.  If <tt>csq</tt> is <tt>null</tt>, then characters
     *         will be appended as if <tt>csq</tt> contained the four
     *         characters <tt>"null"</tt>.
     *
     * @param  start
     *         The index of the first character in the subsequence
     *
     * @param  end
     *         The index of the character following the last character in the
     *         subsequence
     *
     * @return  This writer
     *
     * @throws  IndexOutOfBoundsException
     *          If <tt>start</tt> or <tt>end</tt> are negative, <tt>start</tt>
     *          is greater than <tt>end</tt>, or <tt>end</tt> is greater than
     *          <tt>csq.length()</tt>
     *
     * @since  1.5
     */
    public PrintWriter append(CharSequence csq, int start, int end) {
	CharSequence cs = (csq == null ? "null" : csq);
	write(cs.subSequence(start, end).toString());
    	return this;
    }
    
    /**
     * Appends the specified character to this writer.
     *
     * <p> An invocation of this method of the form <tt>out.append(c)</tt>
     * behaves in exactly the same way as the invocation
     *
     * <pre>
     *     out.write(c) </pre>
     *
     * @param  c
     *         The 16-bit character to append
     *
     * @return  This writer
     *
     * @since 1.5
     */
    public PrintWriter append(char c) {
	write(c);
	return this;
    }
}