11University of Utah – School of Computing

Computer Science 1021 "Applets and Applications"

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22

Methods

• Every method must be called before it can do anything

• Two ways it can be called- By Java (automatically)- By the programmer (explicitly)

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Methods

• Automatically called methods- init()- paint()- actionPerformed()

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Methods

• Manually called methods- JPanel.add(button) // or whatever

- Integer.parseInt()- Math.random()- JTextField.getText()

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55

Methods

• (show example on whiteboard)

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66

Applets: A Review

• Run inside a web browser

• Extend JApplet

• Don't control their own size

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Java Applications

• Run in their own window- (or no window at all!)

• Don't have to "extend" anything- (but most do, anyway)

• Can set their own window size!

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Application Example

• Eclipse!

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Application Example

• Homework 4 as an application- (show demo)

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A Recipe for Applets

• Extend JApplet• Write init() and/or paint() method• Tell Eclipse (or a web page) how big to

make it

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A Recipe for Applications

• Extend JFrame to give us a window• Write a main() method• Tell application:

- How big to make the window- To open the window- What to do when the window closes

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More on methods

• Applets told us what methods to write• Applications don't, except main().• What to do?

- Put all our code inside main()?- Make up our own brand new methods?

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More on methods

• We can write our own methods!• Then it's up to us to call them.

- Java won't call them automatically

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1414

Show and Tell

• Let's look at a simple example together- (you'll get to do one yourself tomorrow)