Escape Sequences Test

/*
 * author: Nick Humphrey, http://nickhumphreyit.blogspot.no/
 * date: 20131202
 *
 * description: testing escape sequences
 *
 * characters, escape sequences:
 * http://docs.oracle.com/javase/tutorial/java/data/characters.html
 *
 * java.util.regex.Pattern:
 * http://docs.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html
 * */
public class EscapeSequencesTest {
    public static void main(String[] args) {
        /*
         * If the number of consecutive backslashes is even (e.g. \\\\...), then the \ is eligible to begin a Unicode
         * escape;
         * if odd, then the \ is not eligible to begin a Unicode escape (e.g. \\\...)
         *
         * OBSERVATION:
         * if number of \ is even, output: (number of \) / 2
         * if number of \ is odd, output: (number of \) % 2 + 1
         */
        System.out.println("\\u2126=\u2126"); // OUT: \u2126=Ω
        System.out.println("\\\\u2126=\\\u2126"); // OUT: \\u2126=\Ω
        System.out.println("\\\\\\u2126=\\\\\u2126"); // OUT: \\\u2126=\\Ω

        /*
         * If an eligible \ is not followed by u, then it is treated as a RawInputCharacter and
         * remains part of the escaped Unicode stream.
         */
        System.out.println("\\\f123"); // OUT: \123 (the unprintable character is "box 000C")
        System.out.println("\\123"); // OUT: \123

        /*
         * If an eligible \ is followed by u, or more than one u, and the last u is not followed
         * by four hexadecimal digits, then a compile-time error occurs.
         *
         * OUT: Exception in thread "main" java.lang.Error: Unresolved compilation problem: Invalid unicode
         */
//      System.out.println("\ uu123"); // (but without a space between "\" and "u"--otherwise eclipse gives an error)

        /*
         * For example, the raw input \u005cu005a results in the six characters \ u 0 0 5 a,
         * because 005c is the Unicode value for \
         *
         * OUT:
         * Exception in thread "main" java.lang.Error: Unresolved compilation problems:
         * Invalid unicode
         * Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
         */
//      System.out.println("\u005cu005a");

        /*
         * regexp:
         * http://docs.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html
         *
         * (EXAMPLES IN THE LIST BELOW SHOULD BE WITHOUT A SPACE BETWEEN \ AND FIRST CONTIGUOUS CHAR.
         * SPACES ARE INSERTED SO THE FILE WOULD COMPILE)
         * The character with octal value 0n (0 <= n <= 7)
         * \0n
         * The character with octal value 0nn (0 <= n <= 7)
         * \0nn
         * The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7)
         * \0mnn
         * The character with hexadecimal value 0xhh
         * \ xhh
         * The character with hexadecimal value 0xhhhh
         * \ uhhhh
         * The tab character ('\u0009')
         * \t
         * The newline (line feed) character (' ')
         * \n
         * The carriage-return character (' ')
         * \r
         * The form-feed character ('\u000C')
         * \f
         * The alert (bell) character ('\u0007')
         * \a
         * The escape character ('\u001B')
         * \e
         * The control character corresponding to x
         * \ cx
         */

        // The character with octal value 0n (0 <= n <= 7)
        System.out.println("\00"); // OUT: (blank/nothing)
        System.out.println("\01"); // OUT: 

        System.out.println("\08"); // OUT: (blank/nothing)

        // The character with octal value 0nn (0 <= n <= 7)
        System.out.println("\0nn"); // OUT: (blank/nothing)
        System.out.println("\007"); // OUT: 

        // The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7)
        System.out.println("\0mnn"); // OUT: (blank/nothing)
        System.out.println("\0207"); // OUT: 7

        // The character with hexadecimal value 0xhh
//      System.out.println("\xhh");
//      System.out.println("\x0f");
        System.out.println("\0x3d"); // OUT: (blank/nothing)

        // The character with hexadecimal value 0xhhhh
//      System.out.println("\ uhhhh");
        System.out.println("\u0fa4"); // OUT: -ྤ
        System.out.println("\0u0fa4"); // OUT: (blank/nothing)
        System.out.println("\0x0fa4"); // OUT: (blank/nothing)

        // The tab character ('\u0009')
        System.out.println("\t"); // OUT: (tab)

        // The newline (line feed) character,

        System.out.println("\n"); // OUT: (new line)

        // The carriage-return character,
        System.out.println("\r"); // OUT: (blank/nothing)

        // The form-feed character ('\u000C')
        // NOTE: ('\u000C') in the comment doesn't give compile errors like examples above, e.g., '\ u000D' (but without a space between "\" and "u"--otherwise eclipse gives an error)
        System.out.println("\f"); // OUT:

        // The alert (bell) character ('\u0007')
        /*
         * COMPILE ERROR: Got an exception - unexpected char: 'a'
         * CAUSE: checkstyle
         * FIX: right click in file > checkstyle > clear checkstyle violations
         *
         * COMPILE ERROR: Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
         */
//      System.out.println("\a");

        // The escape character ('\u001B')
        // COMPILE ERROR: Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
//      System.out.println("\e");

        // The control character corresponding to x
        // COMPILE ERROR: Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
//      System.out.println("\cX");
//      System.out.println("\c?");
//      System.out.println("\c0");
//      System.out.println("\cf");
//      System.out.println("\cB");

        /*
         * characters, escape sequences:
         * http://docs.oracle.com/javase/tutorial/java/data/characters.html
         */
        // \b  Insert a backspace in the text at this point.
        System.out.println("x\b"); // OUT: x

        System.out.println("\1"); // OUT: 


        char character = 'a';
        int ascii = (int) character;
        System.out.println(ascii); // OUT: 97
        System.out.println("\097"); // OUT:
        System.out.println("\123"); // OUT: S
        System.out.println("\124"); // OUT: T
        System.out.println("\1234567890"); // OUT: S4567890

        /*
         * OUT:
         * (empty/new line)
         * 3
         */
        System.out.println("\0123");

        /*
         * OUT:
         * Exception in thread "main" java.lang.Error: Unresolved compilation problem:
         * Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
         */
//      System.out.println("\ 256");    // compile error when uncommented

        /*
         * OUT:
         * (empty/new line)
         * É
         */
        System.out.println("\12\311");

        System.out.println("--"); // control output, to denote last line
    }
}