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2010-06-01T05:19:21Z

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в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== A PrintWriter that also sends its output to a log stream ==



<source lang="java">
/*
* Copyright 2005 Joe Walker
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.BufferedWriter;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;
import org.apache.rumons.logging.LogFactory;
import org.apache.rumons.logging.Log;
/**
* A PrintWriter that also sends its output to a log stream
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class DebuggingPrintWriter extends PrintWriter
{
/**
* Create a new PrintWriter, without automatic line flushing.
* @param prefix A tag to prefix lines with for debugging purposes
* @param out A character-output stream
*/
public DebuggingPrintWriter(String prefix, Writer out)
{
super(out, false);
this.prefix = prefix;
}
/**
* Create a new PrintWriter.
* @param prefix A tag to prefix lines with for debugging purposes
* @param out A character-output stream
* @param autoFlush A boolean; if true, the println() methods will flush the output buffer
*/
public DebuggingPrintWriter(String prefix, Writer out, boolean autoFlush)
{
super(out, autoFlush);
this.prefix = prefix;
}
/**
* 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 prefix A tag to prefix lines with for debugging purposes
* @param out An output stream
* @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
*/
public DebuggingPrintWriter(String prefix, OutputStream out)
{
super(out, false);
this.prefix = prefix;
}
/**
* 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 prefix A tag to prefix lines with for debugging purposes
* @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 DebuggingPrintWriter(String prefix, OutputStream out, boolean autoFlush)
{
super(new BufferedWriter(new OutputStreamWriter(out)), autoFlush);
this.prefix = prefix;
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(boolean)
*/
@Override
public void print(boolean x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(char)
*/
@Override
public void print(char x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(int)
*/
@Override
public void print(int x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(long)
*/
@Override
public void print(long x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(float)
*/
@Override
public void print(float x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(double)
*/
@Override
public void print(double x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(char[])
*/
@Override
public void print(char[] x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(java.lang.String)
*/
@Override
public void print(String x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#print(java.lang.Object)
*/
@Override
public void print(Object x)
{
super.print(x);
buffer.append(x);
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println()
*/
@Override
public void println()
{
synchronized (lock)
{
printBuffer();
super.println();
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(boolean)
*/
@Override
public void println(boolean x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(char)
*/
@Override
public void println(char x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(int)
*/
@Override
public void println(int x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(long)
*/
@Override
public void println(long x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(float)
*/
@Override
public void println(float x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(double)
*/
@Override
public void println(double x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(char[])
*/
@Override
public void println(char[] x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(java.lang.String)
*/
@Override
public void println(String x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/* (non-Javadoc)
* @see java.io.PrintWriter#println(java.lang.Object)
*/
@Override
public void println(Object x)
{
synchronized (lock)
{
printBuffer();
super.println(x);
}
}
/**
* Write the characters in the print buffer out to the stream
*/
private void printBuffer()
{
if (buffer.length() > 0)
{
log.debug(prefix + buffer.toString());
buffer.setLength(0);
}
}
/**
* How to we prefix all the debugging lines?
* @return the prefix
*/
public String getPrefix()
{
return prefix;
}
/**
* How to we prefix all the debugging lines?
* @param prefix the prefix to set
*/
public void setPrefix(String prefix)
{
this.prefix = prefix;
}
/**
* How to we prefix all the debugging lines?
*/
private String prefix;
/**
* A buffer where we store stuff before a newline
*/
protected final StringBuffer buffer = new StringBuffer();
/**
* The log stream
*/
private static final Log log = LogFactory.getLog(DebuggingPrintWriter.class);
}</source>



== A PrintWriter that ends lines with a carriage return-line feed (CRLF). ==



<source lang="java">
/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
/**
* A <tt>PrintWriter</tt> that ends lines with a carriage return-line feed (<tt>CRLF</tt>).
*
* <h3>Concurrency</h3>
* This class is <b>as</b> synchronized as <tt>PrintWriter</tt>.
*
* @version <tt>$Revision: 1958 $</tt>
* @author
*/
public class CRLFPrintWriter extends PrintWriter {
protected boolean autoFlush = false;
public CRLFPrintWriter(final Writer out) {
super(out);
}
public CRLFPrintWriter(final Writer out, final boolean autoFlush) {
super(out, autoFlush);
this.autoFlush = autoFlush;
}
public CRLFPrintWriter(final OutputStream out) {
super(out);
}
public CRLFPrintWriter(final OutputStream out, final boolean autoFlush) {
super(out, autoFlush);
this.autoFlush = autoFlush;
}
protected void ensureOpen() throws IOException {
if (out == null)
throw new IOException("Stream closed");
}
public void println() {
try {
synchronized (lock) {
ensureOpen();
out.write("\r\n");
if (autoFlush) {
out.flush();
}
}
} catch (InterruptedIOException e) {
Thread.currentThread().interrupt();
} catch (IOException e) {
setError();
}
}
}</source>



== PrintWriter ==

<OL><LI>PrintWriter is a better alternative to OutputStreamWriter and FileWriter.</LI><LI>PrintWriter allows you to choose an encoding by passing the encoding information to one of its constructors.</LI></OL>



<source lang="java">
public PrintWriter (File file)
public PrintWriter (File file, String characterSet)
public PrintWriter (String filepath)
public PrintWriter (String filepath, String ccharacterSet)
public PrintWriter (OutputStream out)
public PrintWriter (Writer out)</source>



== PrintWriter is more convenient to work with than OutputStreamWriter ==

<p>It adds nine print method overloads that allow you to output any type of Java primitives and objects.</p>



<source lang="java">
public void print (boolean b)
public void print (char c)
public void print (char[] s)
public void print (double d)
public void print (float f)
public void print (int i)
public void print (long l)
public void print (Object object)
public void print (String string)</source>



<p>There are also nine println method overloads, which rint a new line character after printing the argument.
In addition, there are two format method overloads that enable you to print according to a print format.</p>

== Turn System.out into a PrintWriter. ==



<source lang="java">
import java.io.PrintWriter;
public class MainClass {
public static void main(String[] args) {
PrintWriter out = new PrintWriter(System.out, true);
out.println("Hello, world");
}
}</source>



== Using PrintWriter ==



<source lang="java">
import java.io.IOException;
import java.io.PrintWriter;
public class MainClass {
public static void main(String[] args) {
try {
PrintWriter pw = new PrintWriter("c:\\temp\\printWriterOutput.txt");
pw.println("PrintWriter is easy to use.");
pw.println(1234);
pw.close();
} catch (IOException e) {
}
}
}</source>



== Write lines of text to file using a PrintWriter ==



<source lang="java">
import java.io.FileWriter;
import java.io.PrintWriter;
public class Main {
public static void main(String[] args) throws Exception {
String filename = "fileName.txt";
String[] linesToWrite = new String[] { "a", "b" };
boolean appendToFile = true;
PrintWriter pw = null;
if (appendToFile) {
pw = new PrintWriter(new FileWriter(filename, true));
} else {
pw = new PrintWriter(new FileWriter(filename));
// pw = new PrintWriter(new FileWriter(filename, false));
}
for (int i = 0; i < linesToWrite.length; i++) {
pw.println(linesToWrite[i]);
}
pw.flush();
pw.close();
}
}</source>

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Admin: 1 версия

в 17:44, 31 мая 2010