Java Tutorial/Data Type/Escape Sequences

Character Escape Sequences

A backslash indicates the start of an escape sequence.

An escape sequence for a Unicode character: adding "\u" in front of the code

Website for unicode http://www.unicode.org/

public class MainClass{
  public static void main(String[] arg){
     char myCharacter = "\u0058";
     
     System.out.println(myCharacter);
  }
}

X

Convert lines into the canonical format, that is, terminate lines with the CRLF sequence.

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
 * Convert lines into the canonical format, that is, terminate lines with the
 * CRLF sequence.
 * 
 * @author John Mani
 */
public class CRLFOutputStream extends FilterOutputStream {
  protected int lastb = -1;
  protected boolean atBOL = true; // at beginning of line?
  private static final byte[] newline = { (byte) "\r", (byte) "\n" };
  public CRLFOutputStream(OutputStream os) {
    super(os);
  }
  public void write(int b) throws IOException {
    if (b == "\r") {
      writeln();
    } else if (b == "\n") {
      if (lastb != "\r")
        writeln();
    } else {
      out.write(b);
      atBOL = false;
    }
    lastb = b;
  }
  public void write(byte b[]) throws IOException {
    write(b, 0, b.length);
  }
  public void write(byte b[], int off, int len) throws IOException {
    int start = off;
    len += off;
    for (int i = start; i < len; i++) {
      if (b[i] == "\r") {
        out.write(b, start, i - start);
        writeln();
        start = i + 1;
      } else if (b[i] == "\n") {
        if (lastb != "\r") {
          out.write(b, start, i - start);
          writeln();
        }
        start = i + 1;
      }
      lastb = b[i];
    }
    if ((len - start) > 0) {
      out.write(b, start, len - start);
      atBOL = false;
    }
  }
  /*
   * Just write out a new line, something similar to out.println()
   */
  public void writeln() throws IOException {
    out.write(newline);
    atBOL = true;
  }
}

Determines if this is a quoted argumented - either single or double quoted.

import java.io.File;
/* 
 * 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.
 *
 *@author 
 */
public class Main {
  private static final String SINGLE_QUOTE = "\"";
  private static final String DOUBLE_QUOTE = "\"";
  private static final char SLASH_CHAR = "/";
  private static final char BACKSLASH_CHAR = "\\";
 
  /**
   * Determines if this is a quoted argumented - either single or
   * double quoted.
   *
   * @param argument the argument to check
   * @return true when the argument is quoted
   */
  public static boolean isQuoted(final String argument) {
      return ( argument.startsWith( SINGLE_QUOTE ) || argument.startsWith( DOUBLE_QUOTE ) ) &&
          ( argument.endsWith( SINGLE_QUOTE ) || argument.endsWith( DOUBLE_QUOTE ) );
  }
}

Returns the quoted version of the string using the quotechar argument.

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringWriter;
/* Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * 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 the Hypersonic SQL Group 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 HYPERSONIC SQL GROUP,
 * 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.
 *
 * This software consists of voluntary contributions made by many individuals
 * on behalf of the Hypersonic SQL Group.
 *
 *
 * For work added by the HSQL Development Group:
 *
 * Copyright (c) 2001-2009, The HSQL Development Group
 * 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 the HSQL Development Group 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 HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * 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.
 */
/**
 * Collection of static methods for converting strings between different formats
 * and to and from byte arrays.
 * 
 * 
 * Includes some methods based on Hypersonic code as indicated.
 * 
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 1.9.0
 * @since 1.7.2
 */
public class Main {
  /**
   * Returns the quoted version of the string using the quotechar argument.
   * doublequote argument indicates whether each instance of quotechar inside
   * the string is doubled.
   *
   * null string argument returns null. If the caller needs the literal
   * "NULL" it should created it itself
   *
   * @param s Java string
   * @param quoteChar character used for quoting
   * @param extraQuote true if quoteChar itself should be repeated
   * @return String
   */
  public static String toQuotedString(String s, char quoteChar,
                                      boolean extraQuote) {
      if (s == null) {
          return null;
      }
      int    count = extraQuote ? count(s, quoteChar)
                                : 0;
      int    len   = s.length();
      char[] b     = new char[2 + count + len];
      int    i     = 0;
      int    j     = 0;
      b[j++] = quoteChar;
      for (; i < len; i++) {
          char c = s.charAt(i);
          b[j++] = c;
          if (extraQuote && c == quoteChar) {
              b[j++] = c;
          }
      }
      b[j] = quoteChar;
      return new String(b);
  }
  /**
   * Counts Character c in String s
   *
   * @param s Java string
   * @param c character to count
   * @return int count
   */
  static int count(final String s, final char c) {
      int pos   = 0;
      int count = 0;
      if (s != null) {
          while ((pos = s.indexOf(c, pos)) > -1) {
              count++;
              pos++;
          }
      }
      return count;
  }
}

Table for escape sequence character

ValueMeaning\bBackspace\fForm feed\nNew line\rCarriage return\tTab

public class MainClass{
  public static void main(String[] arg){
     System.out.println("\b"); 
     System.out.println("\f"); 
     System.out.println("\n"); 
     System.out.println("\r"); 
     System.out.println("\t"); 
  }
}

\\: to specify a backslash character as a character literal or in a text string

public class MainClass {
  public static void main(String[] arg) {
    System.out.println("\\");
    System.out.println("\\\\");
  }
}

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