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Java Forum / First Aid / November 2005Newbie - App button only works once
I have what is meant to be a "humorous" application whereby when the user clicks the "New Cliche" button they receive a new, trite, business cliche. This is adopted from one of the examples in the "Head First Java" book. Anyway, it works but only for one click. When the user clicks the first time, the text field populates with a cliche. The second click however does not change the saying which is what I would like it to do. Can someone offer a suggestion on what I can do to make it change *each* time the user clicks the button. Thank you very much. import java.awt.event.*; import javax.swing.*; import java.awt.*; //implements the action listener interface class WorkCliches extends JFrame implements ActionListener { JButton b1 = new JButton("New Cliche"); JTextField mySaying = new JTextField("", 34); PhraseOMatic myPhrase = new PhraseOMatic(); public WorkCliches() { super("Sayings to Look Smart"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //the next two lines add action listeners //to both JButton objects b1.addActionListener(this); FlowLayout flow = new FlowLayout(FlowLayout.LEFT); setSize(450, 120); setLayout(flow); add(b1); add(mySaying); setVisible(true); } public void actionPerformed(ActionEvent evt) { //evt object's getSource() method determines //the source of the event. Object source = evt.getSource(); if (source == b1) { mySaying.setText(myPhrase.phrase); } } public static void main(String[] args) { WorkCliches frame = new WorkCliches(); } } Have you checked to make sure that myPhrase.phrase is giving you a new phrase? Yes. When I close out the app and re-start it, that first click gives me a different phrase from the first time. Every time that I restart the app - it gives me a different phrase so I think my random from an array is working. Here is the code to the "phrase-o-matic" after I tweaked it. Thanks. class PhraseOMatic { //Three sets of words to choose from String[] wordListOne = { "24/7", "multi-Tier", "30,000 foot", "B-to-B", "win-win", "front-end","web-based", "pervasive", "smart", "six-sigma", "critical-path", "dynamic" }; String[] wordListTwo = { "Empowered", "sticky", "value-added", "oriented", "centric", "distributed","clustered", "branded", "outside-the-box", "positioned", "networked", "focused", "leveraged", "aligned", "targeted", "shared", "cooperative", "accelerated" }; String[] wordListThree = { "process", "tipping-point", "solution", "architecture", "core competency", "strategy","mindshare", "portal", "space", "vision", "paradigm", "mission" }; //how many words in each list int oneLength = wordListOne.length; int twoLength = wordListTwo.length; int threeLength = wordListThree.length; //generate three random numbers int rand1 = (int) (Math.random() * oneLength); int rand2 = (int) (Math.random() * twoLength); int rand3 = (int) (Math.random() * threeLength); //build a phrase String phrase = wordListOne[rand1] + " " + wordListTwo[rand2] + " " + wordListThree[rand3]; } I would recommend changing your setText to a simple print out inside the actionPerformed so that you can make sure that a new call to myPhrase.phrase gives you a new phrase. System.out.println(myPhrase.phrase); Thanks but when I tried your suggestion, it placed the results in the console at the bottom of the screen instead of the application itself. Also, unfortunately, it did not change the phrase. Everytime I clicked the button it repeated the same phrase over and over in the console area. I appreciate the help though. > Thanks but when I tried your suggestion, it placed the results in > the console at the bottom of the screen instead of the application > itself. Also, unfortunately, it did not change the phrase. > Everytime I clicked the button it repeated the same phrase over and > over in the console area. I appreciate the help though. I believe the person to whom you were referring meant the results to be placed on the console, not the gui. This way you can check to see if your random phrase generator is working properly without worrying about issues of refreshing, etc. It's just one step in trying to narrow down the root cause of the bug. By the way, it's a lot easier to follow a discussion and figure out what's going on if you quote the relevant sections of the previous post.  Signaturemonique Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html After looking at the code in PhraseOMatic, the problem is that you only generate one random number. When you call myPhrase.phrase, it will pick up the same one each time. What you need to do is create a method in PhraseOMatic that will generate a random phrase, and then call that method. I meant to say one random phrase. > After looking at the code in PhraseOMatic, the problem is that you only > generate one random number. Indeed. You want to alter your PhraseOMatic class a bit. /* * NOTE: untested code */ class PhraseOMatic { Random random = new Random(); //Three sets of words to choose from String[] wordListOne = { "24/7", "multi-Tier", "30,000 foot", "B-to-B", "win-win", "front-end","web-based", "pervasive", "smart", "six-sigma", "critical-path", "dynamic"}; String[] wordListTwo = { "Empowered", "sticky", "value-added", "oriented", "centric", "distributed","clustered", "branded", "outside-the-box", "positioned", "networked", "focused", "leveraged", "aligned", "targeted", "shared", "cooperative", "accelerated"}; String[] wordListThree = { "process", "tipping-point", "solution", "architecture", "core competency", "strategy","mindshare", "portal", "space", "vision", "paradigm", "mission"}; public String getNewPhrase() { StringBuffer buffer = new StringBuffer(); buffer.append(wordListOne[random.nextInt(wordListOne.length - 1)]); buffer.append(wordListTwo[random.nextInt(wordListTwo.length - 1)]); buffer.append(wordListThree[random.nextInt(wordListThree.length - 1)]); return buffer.toString(); } } Then in your actionPerformed method: mySaying.setText(myPhrase.getNewPhrase()); Note how I used the java.util.Random instead of Math.random(). If you want to read why this is better, read http://mindprod.com/jgloss/gotchas.html#RANDOM Kind regards, Jonck > buffer.append(wordListOne[random.nextInt(wordListOne.length - 1)]); > buffer.append(wordListTwo[random.nextInt(wordListTwo.length - 1)]); > buffer.append(wordListThree[random.nextInt(wordListThree.length - 1)]); Small correction, the -1 should be left out, since nextInt produces numbers from 0 to n-1 instead of from 0 to n (as my code assumed). ah man - I'm happy. It now works as envisioned! Thanks everyone. (I'm lovin' this java thing.) > Note how I used the java.util.Random instead of Math.random(). If you > want to read why this is better, read > http://mindprod.com/jgloss/gotchas.html#RANDOM I took a look at the page and I couldn't see why using java.util.Random is better than Math.random(). Can you elaborate? - Oliver > I took a look at the page and I couldn't see why using java.util.Random > is better than Math.random(). Can you elaborate? Hmm... I was under the impression that Math.Random created "less random" numbers (and that I had read that at Roedy's site) but I can't find it anywhere anymore. I guess either my memory is mistaken or I read it elsewhere. Should I find the source I'll post it here. > I took a look at the page and I couldn't see why using java.util.Random > is better than Math.random(). Can you elaborate? Well, I can't find the source, but here is how I remember it to be. The Math.random() function seeds itself with the current time in milliseconds. Thus, if you call Math.random() three times in a row, there is the possibility that you will with the same seed each time and get the same number as a result. In comparison, if you create a java.util.Random object and call nextInt 3 times in a row, you will be working with one seed and getting the next three numbers derived from it, thus making things more random. But I could be wrong, this is how I remember it, but I can't find a source to corroborate. > Well, I can't find the source, but here is how I remember it to be. The > Math.random() function seeds itself with the current time in [quoted text clipped - 7 lines] > But I could be wrong, this is how I remember it, but I can't find a > source to corroborate. From the Javadocs @ http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Math.html#random() <quote> When this method is first called, it creates a single new pseudorandom-number generator, exactly as if by the expression new java.util.Random This new pseudorandom-number generator is used thereafter for all calls to this method and is used nowhere else. </quote> So it looks like Math.random() seeds the random number generator once (the first time it's used), and never re-seeds it again (special issues regarding custom class loaders not withstanding). I usually instantiate my own RNG instead of using Math.random() anyway, but still it would have been nice to know if Math.random() really did have a flaw. - Oliver > So it looks like Math.random() seeds the random number generator once > (the first time it's used), and never re-seeds it again (special issues > regarding custom class loaders not withstanding). Ok, thanks for putting me in the right. <jonck@vanderkogel.net> wrote... >> I took a look at the page and I couldn't see why using >> java.util.Random is better than Math.random(). Can you elaborate? [quoted text clipped - 3 lines] > find it anywhere anymore. I guess either my memory is mistaken or I > read it elsewhere. Should I find the source I'll post it here. It could never create "less random" numbers than using java.util.Random, as Math.Random *uses* java.util.Random behind the scenes. It's just a "convenience" method. However, java.util.Random *itself* is not perfect and creates "less random" numbers than *other* random number generators, which is discussed on Roedy's page. // Bjorn A > I took a look at the page and I couldn't see why using java.util.Random >is better than Math.random(). Can you elaborate? you have control over the seeding. This can be useful in debugging if you want to reproduce a run. Math.random just gives you a double. java.util.Random has a richer set of methods. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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