printwriter.java

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/*
 * @(#)PrintWriter.java	1.32 06/10/13
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;


/**
 * Print formatted representations of objects to a text-output stream.  This
 * class implements all of the print methods found in PrintStream.  It does not
 * contain methods for writing raw bytes, for which a program should use
 * unencoded byte streams.
 *
 * <p> Unlike the PrintStream class, if automatic flushing is enabled it will
 * be done only when one of the println() methods is invoked, rather than
 * whenever a newline character happens to be output.  The println() 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.  The client may
 * inquire as to whether any errors have occurred by invoking checkError().
 *
 * @version 	1.24, 02/02/00
 * @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;

    /**
     * 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 println() 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 println() 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);
    }

    /** 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;
    }


    /*
     * 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();
	    }
	}