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Communicating Boolean values (true/false) between humans and computer

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• Representing Boolean values in computer
  • There are 2 Boolean values in Java:

    true (Internally (= inside the computer program), the value true is represented by the binary number 1) false (Internally (= inside the computer program), the value false is represented by the binary number 0)

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    Example:

    boolean x; x = true;

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• Representing Boolean values on key boards/terminal for humans
  • How the Java programming language print Boolean values:

    If a boolean variable contains the boolean value true, Java will print the string ``true'' The string ``true'' consists of the 4 ASCII codes for the characters 't', 'r', 'u' and 'e' !!!         If a boolean variable contains the boolean value false, Java will print the string ``false'' The string ``true'' consists of the 5 ASCII codes for the characters 'f', 'a', 'l', 's' and 'e' !!!         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:

    Humans will enter/see the strings "true"/"false" (i.e.: ASCII codes on the key board/monitor and associate them with the Boolean values true/false !!! Internally (= inside a Java program, the boolean values are represented by the values true (= binary number 1) and false (= binary number 0)

    We need to convert between these 2 different representations....

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• Converting between ASCII representation of boolean values and the internal boolean representation
  • Java provides library methods to convert between the "ASCII" representation of the boolean values and 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", we return true If s == "false", we return false String toString( boolean x ): return a String that represents the boolean value x If x == true, we return "true" If x == false, we return false

    See: click here

    The method parseBoolean( ) performs the following translation:

    Input Output -------- ------------- "true" ---> true (= 1) "false" ---> false (= 1)

    The method toString( ) performs the following translation:

    Input Output ----------- ------------- true (= 1) ---> "true" false (= 0) ---> "false"

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  • These methods are very simple and I like to use them to show you a simple example of conversion between 2 different representations

    We write these methods to convert between the representations used by humans and the computer below

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• The conversion methods in Java
  • The conversion methods from "program" Boolean values to String Boolean representations are as follows:

    public class BooleanIO // I need to add IO to the name because the Boolean class // is already defined inside the Java standard library { public static boolean parseBoolean( String s ) { if ( s.equals("true") ) return true; else return false; } public static String toString( boolean x ) { if ( x == true ) return "true"; else return "false"; } }

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  • Here's a program that show to use parseBoolean() (to allow a user to enter a Boolean value to the computer)

    Scanner in = new Scanner( System.in ); String input; boolean x; System.out.print("Enter a boolean value: "); input = in.nextLine(); x = BooleanIO.parseBoolean(input);

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  • Example Program: (Demo above code)                                                
    • The class that contains the conversion methods: click here
    • The BooleanDemo test Prog file: click here

    How to run the program:

    Right click on link and save in a scratch directory To compile:   javac BooleanDemo.java To run:          java BooleanDemo

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• Postscript
  • The Java library already has these methods !!

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  • You can use this instead:

    boolean x; x = Boolean.parseBoolean( "true" ); or x = Boolean.parseBoolean( "false" );

    See: click here