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Thread: JOptionPane and StringBuilder

  1. #1
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    Question JOptionPane and StringBuilder

    I'm using the JOptionPane to display and receive information to/from the user. In addition to this, I am using StringBuilder to receive inputs from the user and then manipulate (append) that input to display the desired output.
    //Example

    (JOptionPane): "Enter text"

    (user input): Java is cool!

    (program): *stringBuilder.append(" I love it!")

    JOptionPane.showMessageDialog( );

    .....

    Hopefully you get the idea from this psuedo-like code. The problem is that showMessageDialog(null, string) and not showMessageDialog(string, string). I want to display the enter text: " Java is cool! I love it! " in the JOptionPane. How do I accomplish this, since showMessageDialog only accepts (null, string).


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: JOptionPane and StringBuilder

    problem is that showMessageDialog(null, string) and not showMessageDialog(string, string)
    Why can't you use the version that works with a single String? What is the reason you think you need two Strings?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: JOptionPane and StringBuilder

    If I want to show the first text "Java is cool!" using JOptionPane, then append.("I love it!) to the text, "Java is cool!" does not appear. So I assumed I needed to use (string, stringBuilder.toString() ) instead of (null, stringBuilder.toString() )

    public class builderMain {
     
    	public static void main(String[] args) {
    		String hello = JOptionPane.showInputDialog( null, "Enter Text" , "String Builder", JOptionPane.INFORMATION_MESSAGE);
    		JOptionPane.showMessageDialog(null, hello, "String Builder", JOptionPane.INFORMATION_MESSAGE);
     
    		StringBuilder stringBuilder = new StringBuilder();
     
    		//stringBuilder.append("");
    		stringBuilder.append( " I love it!" );
    		stringBuilder.capacity();
     
    		JOptionPane.showMessageDialog( null, stringBuilder.toString() , "String Builder", JOptionPane.INFORMATION_MESSAGE);
     
    		String yes =JOptionPane.showInputDialog(null, "Enter the string ' Yes, '");
    		stringBuilder.insert(16, yes);
    		JOptionPane.showMessageDialog( null, stringBuilder.toString() , "String Builder", JOptionPane.INFORMATION_MESSAGE);

    Why does " Java is cool! " not remain in the stringBuilder when I compile? It says, "I love Yes, it!"
    Last edited by javaStooge; March 6th, 2014 at 09:29 PM.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: JOptionPane and StringBuilder

    I don't see where the code is appending the String: "I love it!" to the String: "Java is cool!"?
    Either use the + operator to concatenate the two Strings
    or put them both into StringBuilder and use its toString() method to get the String with them both in it.
    If you don't understand my answer, don't ignore it, ask a question.

  5. The Following User Says Thank You to Norm For This Useful Post:

    javaStooge (March 6th, 2014)

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    Default Re: JOptionPane and StringBuilder

    I see where my error is... StringBuilder stringBuilder = new StringBuilder(hello);

    I didn't assign an initial value (hello) in the constructor...

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