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IC211 Lecture 8

IC211 Lecture 8. I/O: Command Line And JOptionPane. Outline. Review Project 1 Specification A Review of Scope Command Line Input Wrapper Classes (Integer, Double, etc) I/O with JOptionPane. Scope. Same as C++ Variable exists only within the block where it was declared

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IC211 Lecture 8

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  1. IC211Lecture 8 I/O: Command Line And JOptionPane

  2. Outline • Review Project 1 Specification • A Review of Scope • Command Line Input • Wrapper Classes (Integer, Double, etc) • I/O with JOptionPane

  3. Scope • Same as C++ • Variable exists only within the block where it was declared • Duplicate variable names within the same class file • Example: execution class from Lab 4 • Example: scope worksheet

  4. Both are Strings! Command Line Input • Core Java 2 pg 84 • public static void main (String[] args) • args contains arguments from the command line • Ex: MakeShape –c 3.5 args[0]: -c args[1]: 3.5

  5. Converting Strings to Numbers(Wrapper Classes) • Used to convert primitive types to Objects. • Wrapper classes (Core Java pg 186) • Double, Float, Integer, Long, Short, Byte, Character, Boolean • Some containers only hold objects, not primitives • Can also be used to convert Strings to numbers • Need to convert String representation 3.5 to numeric 3.5 • Double.parseDouble(String s) • Java SE 6 API • Ex: MakeShape.java

  6. Comparing Integers, Doubles, etc.for Equality Scanner in = new Scanner(System.in); System.out.println("Enter two integers: "); Integer a = new Integer(in.nextInt()); Integer b = new Integer(in.nextInt()); if (a == b) System.out.println("Same!"); else System.out.println("Different!"); Enter two integers: 100 100 Output> ??? Output> Different! Must use .equals() method vice ==, just like we do with Strings

  7. JOptionPane • Create message or dialog boxes without overhead of full GUI application • Get input from the user with an input dialog box String name = JOptionPane.showInputDialog("What's your name?"); • Part of the javax.swing package

  8. JOptionPane • Getting numeric input…must still use and input dialog box String input = JOptionPane.showInputDialog("Guess a number from 0 to 100"); Convert String input to numeric using wrapper classes int number = Integer.parseInt(input);

  9. JOptionPane • Display a message with a message dialog box JOptionPane.showMessageDialog(null, "Welcome to IC211!");

  10. JOptionPane • Getting a confirmation (yes/no) with a confirmation dialog box int done = JOptionPane.showConfirmDialog(null, “Are you finished?”); Returns an int equal to one of three static constants: • JOptionPane.YES_OPTION • JOptionPane.NO_OPTION • JOptionPane.CANCEL_OPTION

  11. JOptionPane Example(Number Game) • Guess a number from 0 to 100 • Version using console input (Scanner) • JOptionPane version

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