Java Programming :: How to solve this problem of initialization


	How to solve this problem of initialization / Create JradioButton and add to jrpnlRadBtn String temp[] = {"Compilers","Operating Systems","Computer Networks"}; JRadioButton jrbtnSub[]; for(int i=0;i<3;i++) { jrbtnSub[i] = new JRadioButton(temp[i]); jpnlRadBtn.add(jrbtnSub[i]); } Above code snippet gives the error: JRadioButtonDemo.java:22: variable jrbtnSub might not have been initialized jrbtnSub[i] = new JRadioButton(temp[i]); Ravi wrote: > / Create JradioButton and add to jrpnlRadBtn > String temp[] = {"Compilers","Operating > Systems","Computer Networks"}; > JRadioButton jrbtnSub[]; This says: "jrbtnSub is a variable that can refer to arrays of JRadioButton references." It does not actually create an array, it just says that jrbtnSub can refer to one if you ever decide to create one. For example, you might continue with jrbtnSub = new JRadioButton[3]; // or perhaps more to create a three-element array and set jrbtnSub to point at it. Or you could declare and initialize in one line with JRadioButton[] jrbtnSub = new JRadioButton[3]; (Stylistic note: Most Java practitioners prefer `SomeType[] arrayRef' over `SomeType arrayRef[]', although both forms are legal. It is felt that the first form collects all the type information in one place, while the second spreads it out in separate chunks. Using the second form also calls into question one's dedication to Java by showing that one has not yet fully renounced C!) -- Eric Sosman esos@acm-dot-org.invalid "Ravi" <ra.ravi.@gmail.com> wrote: >/ Create JradioButton and add to jrpnlRadBtn > String temp[] = {"Compilers","Operating > Systems","Computer Networks"}; > JRadioButton jrbtnSub[]; > for(int i=0;i<3;i++) { > jrbtnSub[i] = new JRadioButton(temp[i]); > jpnlRadBtn.add(jrbtnSub[i]); > } > Above code snippet gives the error: JRadioButtonDemo.java:22: variable > jrbtnSub might not have been initialized > jrbtnSub[i] = new JRadioButton(temp[i]); Yup. The more conventional form of the loop might have given you a clue: for(int i = 0; i < jrbtnSub.length; i++) { You need to intialize jrbtnSub. You probably mean something like: JRadioButton jrbtnSub[] = new JRadioButton[temp.length]; -- Adam Maass Ravi wrote: > / Create JradioButton and add to jrpnlRadBtn > String temp[] = {"Compilers","Operating > Systems","Computer Networks"}; > JRadioButton jrbtnSub[]; > for(int i=0;i<3;i++) { > jrbtnSub[i] = new JRadioButton(temp[i]); > jpnlRadBtn.add(jrbtnSub[i]); > } > Above code snippet gives the error: JRadioButtonDemo.java:22: variable > jrbtnSub might not have been initialized > jrbtnSub[i] = new JRadioButton(temp[i]); In addition to what other replies have said, you might consider using a (java.util.)List instead of an array for the buttons. With a List you don't need to know the number of elements when you create it (and there are many other advantages). So your code could become: String[] subjectNames = { "Compilers", "Operating Systems", "Computer Networks" }; List<JRadioButton> subjectButtons = new java.util.ArrayList<JRadioButton>(); for (String name : subjectNames) { JRadioButton button = new JRadioButton(name); subjectButtons.add(button); subjectPanel.add(button); } (I've changed then identifier names, because I find the likes of "jrbtn" unreadable and unhelpful.) Tom Hawtin Ravi wrote: >> / Create JradioButton and add to jrpnlRadBtn Please do not multi-post. No one is able to see who else answered your question or what they said, which is rather rude to the people you want to help you. It is also rude to the people trying to follow the thread for their own edification. So please do not multi-post. Patricia Shanahan gave a good answer over in clj.help, for those of you who missed it over in cjl.programmer: - Hide quoted text - Patricia Shanahan wrote: > Ravi wrote: >>> How about by initializing it? >>> JRadioButton jrbtnSub[] = new JRadioButton[3]; >> Thanks, Patricia, I must confess initially I thought that you've given >> me a wild guess but when I gave it a try it worked!! >> Can you please explain it too. > The error was non-initialization of the array reference. I looked at its > declaration, and the compiler was right, it was not initialized. > Because it is an array reference, it has to be either null or a pointer > to an array of JRadioButton or some subclass of JRadioButton. > I decided to pick an initializer that would let your loop run. > Specifically, I decided to avoid any exceptions on "jrbtnSub[i] = new > JRadioButton(temp[i]);" for i in the range 0 through 2. > That implied the following: > 1. jrbtnSub cannot be null. > 2. jrbtnSub must point to a JRadioButton[], not a subclass array. > 3. jrbtnSub must point to an array with at least three elements. > Since it is a local variable, and there are no references to elements > other than the first three, I decided three elements was enough. > I copied your style of using the literal 3. In my own code, the whole > code fragment would have looked something like this: > // Create JRadioButton and add to jrpnlRadBtn > String[] buttonNames = {"Compilers","Operating Systems", > "Computer Networks"}; > JRadioButton[] buttons = new JRadioButton[buttonNames.length]; > for(int i=0;i<buttonNames.length;i++) { > buttons[i] = new JRadioButton(buttonNames[i]); > jpnlRadBtn.add(buttons[i]); > } > Patricia

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How to solve this problem of initialization