Java/File Input Output/PrintWriter
Содержание
- 1 A helper class for printing indented text
- 2 A PrintWriter that also sends its output to a log stream
- 3 A PrintWriter that ends lines with a carriage return-line feed (CRLF).
- 4 Create PrintWriter from BufferedWriter
- 5 Create PrintWriter from System.out
- 6 Create PrintWriter out of FileWriter
- 7 Write lines of text to file using a PrintWriter
A helper class for printing indented text
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.PrintWriter;
/**
* A helper class for printing indented text
*
* @version $Revision: 1.2 $
*/
public class IndentPrinter {
private int indentLevel;
private String indent;
private PrintWriter out;
public IndentPrinter() {
this(new PrintWriter(System.out), " ");
}
public IndentPrinter(PrintWriter out) {
this(out, " ");
}
public IndentPrinter(PrintWriter out, String indent) {
this.out = out;
this.indent = indent;
}
public void println(Object value) {
out.print(value.toString());
out.println();
}
public void println(String text) {
out.print(text);
out.println();
}
public void print(String text) {
out.print(text);
}
public void printIndent() {
for (int i = 0; i < indentLevel; i++) {
out.print(indent);
}
}
public void println() {
out.println();
}
public void incrementIndent() {
++indentLevel;
}
public void decrementIndent() {
--indentLevel;
}
public int getIndentLevel() {
return indentLevel;
}
public void setIndentLevel(int indentLevel) {
this.indentLevel = indentLevel;
}
public void flush() {
out.flush();
}
}
A PrintWriter that also sends its output to a log stream
/*
* 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);
}
A PrintWriter that ends lines with a carriage return-line feed (CRLF).
/*
* 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();
}
}
}
Create PrintWriter from BufferedWriter
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.PrintWriter;
class MainClass {
public static void main(String args[]) throws Exception {
FileWriter fw = new FileWriter(args[0]);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter pw = new PrintWriter(bw, false);
pw.println(true);
pw.println("A");
pw.println(500);
pw.println(40000L);
pw.println(45.67f);
pw.println(45.67);
pw.println("Hello");
pw.println(new Integer("99"));
pw.close();
}
}
Create PrintWriter from System.out
import java.io.PrintWriter;
class PrintWriterDemo {
public static void main(String args[]) throws Exception {
PrintWriter pw = new PrintWriter(System.out);
// Experiment with some methods
pw.println(true);
pw.println("A");
pw.println(500);
pw.println(40000L);
pw.println(45.67f);
pw.println(45.67);
pw.println("Hello");
pw.println(new Integer("99"));
// Close print writer
pw.close();
}
}
Create PrintWriter out of FileWriter
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Vector;
public class ListOfNumbers {
private Vector<Integer> victor;
private static final int SIZE = 10;
public ListOfNumbers() {
victor = new Vector<Integer>(SIZE);
for (int i = 0; i < SIZE; i++)
victor.addElement(new Integer(i));
}
public void writeList() {
PrintWriter out = null;
try {
System.out.println("Entering try statement");
out = new PrintWriter(new FileWriter("OutFile.txt"));
for (int i = 0; i < SIZE; i++)
out.println("Value at: " + i + " = " + victor.elementAt(i));
} catch (ArrayIndexOutOfBoundsException e) {
System.err.println("Caught ArrayIndexOutOfBoundsException: "
+ e.getMessage());
} catch (IOException e) {
System.err.println("Caught IOException: " + e.getMessage());
} finally {
if (out != null) {
System.out.println("Closing PrintWriter");
out.close();
} else {
System.out.println("PrintWriter not open");
}
}
}
}
Write lines of text to file using a PrintWriter
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();
}
}
