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Entering Boolean inputs into the computer

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• Problem description: how to enter Boolean values into the computer ?
  • Recall that:

    The Boolean value false is represented by the binary number 00000000 The Boolean value true is represented by the binary number 00000001           (See: click here )

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  • Boolean inputs are entered into the computer input by typing the text:

    true or: false

    Problem:

    When you type in the text true the computer will receive these ASCII codes: 01110100 01110010 01110101 01100101 which represents: t r u e The computer will not receive the Boolean representation 00000001 for true !!! See it for yourself: Enter the text "true" or "false":    true See the corresponding binary ASCII codes for the string:    0100100001100101011100100110010100100000011000100110010100100000011100110110010101100011011100100110010101110100001000000110110101100101011100110111001101100001011001110110010101110011001000010010000100110001 Made by @mathias ---- GitHub! source

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  • In other words:

    Human users will enter the boolean value "true" as a string (i.e.: as the ASCII codes for the letters t, r, u and e) But internally (= inside a Java program, the boolean value true is represented by the binary number 00000001

    Therefore: we need to convert the input (ASCII) representation to the internal boolean representation

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• Converting from ASCII representation of boolean values to the internal boolean representation
  • The Java class Boolean provides parseBoolean( ) method to convert an "ASCII" representation of the boolean values to the internal "program" representation of the boolean values:

    boolean parseBoolean( String s ): return a boolean value translated from the input string s If s == "true", function returns true (= 1) If s == "false", function returns false (= 0)

    See: click here

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  • The method parseBoolean( ) performs the following translation:

    Input Output -------- ------------- "true" ---> 00000001 "false" ---> 00000000 Note: "true" means: the ASCII codes 01110100 01110010 01110101 01100101 "false" maens: the ASCII codes 01100110 01100001 01101100 01110011 01100101

    Example:

    boolean x; String input = in.nextLine(); // Read in a string ("true" or "false") x = Boolean.parseBoolean(input); if ( x ) { System.out.println("You have entered the `true' boolean value"); } else { System.out.println("You have entered the `false' boolean value"); }

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  • Example Program: (Demo above code)                                                
    • Prog file: /home/cs255001/demo/java/String2Bool.java

    How to run the program:

    To compile:   javac String2Bool.java          To run: java String2Bool

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• What's inside the parseBoolean( ) method ???

  • The parseBoolean( ) method is very simple and I like to use it to show you a simple example of conversion from String to boolean representation.

    The parseBoolean( ) method is just one if-statement that check for the string "true":

    public static boolean parseBoolean( String s ) { if ( s.equals("true") ) return true; // returns true, which is the same as the bin number 1 else return false; // returns false, which is the same as the bin number 0 }

    Note:

    The expression s.equals("true") will test if the string s contains the 4 ASCII codes that represents the letters 't' 'r' 'u' 'e' !!!

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  • To try it out, edit the BooleanDemo.java program and make this change:

    x = BooleanIO.parseBoolean(input);

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  • Example Program: (Demo above code)                                                
    • Prog file: /home/cs255001/demo/java/BooleanDemo.java

      Change to Boolean class to BooleanIO

    How to run the program:

    To compile:   javac BooleanDemo.java To run:          java BooleanDemo