Using Objects

Java Primitive Data Types 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

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

What is: Java Syntax??

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

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

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

Assignment ageOfDog = 10;

Variable Declarations and Assignment of Values ASSIGNMENT STATEMENTS

Identifiers Rules for identifiers in Java?

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"); } }

Packages package areatester;

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

java.lang.Object: the root of java classes

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

HomeWork P2.1 - Programming Exercise

Graphical User Interfaces GUI Objects

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

Example: Frame Viewer 01: import javax.swing.JFrame; 02: 03: public class EmptyFrameViewer 04: { 05: public static void main(String[] args) 06: { 07: JFrame frame = new JFrame(); 08: 09: frame.setSize(300, 400); 10: frame.setTitle("An Empty Frame"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 12: frame.setVisible(true); 14: } 15: } (page 56 of text) or section 2.11 Example: Frame Viewer

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

See Sun site for greater detail Sun.java

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

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

Object Lessons?