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Using Objects

Using Objects. Java Primitive Data Types. primitive. integral. boolean. floating point. byte char short int long float double. Begin with lowercase letters. Java Reference Types. Reference types:. 1. String 2. Class name.

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Using Objects

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  1. Using Objects

  2. Java Primitive Data Types primitive integral boolean floating point byte char short int long float double Begin with lowercase letters

  3. Java Reference Types Reference types: 1. String 2. Class name

  4. String Methods • int n = greeting.length(); • String bigRiver = river.toUpperCase();

  5. What is: Java Syntax??

  6. data type variable name Variables int total; int count, temp, result; Multiple variables can be created in one declaration

  7. What Does a Variable Declaration Do? int ageOfDog; 4 bytes for ageOfDog

  8. Variables • initial value in the declaration int sum = 0; int base = 32, max = 149;

  9. Assignment ageOfDog = 10;

  10. Variable Declarations and Assignment of Values VARIABLE DECLARATIONS ASSIGNMENT STATEMENTS

  11. Identifiers • Rules for identifiers in Java?

  12. package movetester; import java.awt.Rectangle; public class MoveTester { public static void main(String[] args) { Rectangle box = new Rectangle(5, 10, 20, 30); // Move the rectangle where x becomes 20 and y becomes 35 box.translate(15, 25); // Print information about the moved rectangle System.out.println(box.getX()); System.out.print("y: "); System.out.println(box.getY()); System.out.println("Expected: 35"); } }

  13. Packages • package areatester;

  14. We work with Objects • A fundamental entity in Java. • Objects are “things”

  15. java.lang.Object: the root of java classes

  16. Class Object • Class encapsulates objects • work together (behavior) • Objects have properties:

  17. HomeWork P2.1 - Programming Exercise

  18. Graphical User Interfaces GUI Objects

  19. frame Graphical User Interfaces (GUI): Demonstrates the object concep0t! Content pane used to display objects in a frame

  20. 01:import javax.swing.JFrame; 02: 03:publicclass EmptyFrameViewer 04:{ 05:publicstaticvoidmain(String[] args) 06:{ 07: JFrame frame =newJFrame(); 08: 09: frame.setSize(300,400); 10: frame.setTitle("An Empty Frame"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 12: frame.setVisible(true); 14:} 15:} Example: Frame Viewer

  21. Jframe frame • Point to object frame = new JFrame (name); (creates a class instance)

  22. See Sun site for greater detail Sun.java

  23. Lab 2:Graphical Fun • Using the example in your text book on page 64; Section 2.13: • Create your own FaceViewer Class with a main method that will show a JComponent. • Adjust your Frame to be square • The frame title must contain your name. • Using the FaceComponent example as a guide (page 64; Section 2.13): • Create an Animal Viewer and draw an animal of your choice. • Draw a string that describes the animal • Set colors as desired

  24. Output • Two classes - tested • Upload to the appropriate dropbox Lab Completion

  25. Object Lessons?

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