Introduction to Java 2 Programming

1
Introduction to Java 2 Programming

• Lecture 2
• Java Syntax, Robocode

2
Overview

• Java Syntax
• Quick Overview
• Robocode
• How it works
• Writing Robots
• Anatomy of a Robot
• Practical Exercises

3
Naming

• All Java syntax is case sensitive
• Valid Java names
• Consist of letters, numbers, underscore, and
  dollar
• Names can only start with letter or underscore
• E.g. firstAttribute but not 1stAttribute
• Camel case convention
• Java encourages long, explanatory names
• Start with a lower case letter, with words
  capitalised
• E.g. thisIsCamelCase, andSoIsThisAsWell

4
Classes

• One Java class defined in each .java file
• File name must match the name of the class
• Otherwise there will be compilation errors
• Class names start with an upper case letter
• Compiler will generate a .class file with same
  name
• Contains the bytecode
• Classes defined using the class keyword.

5
Packages

• Group related classes together
• Each class in a package must have a unique name
• Indicate the package a class belongs to with the
  package keyword
• Recommended each class is put in a package
• Gain access to public classes in other packages
  using the import keyword
• The JVM needs to know where the classes are
  defined before you can use them

6
Anatomy of a Java Source File

• package intro2java
• import java.util.
• /
• A description of the class
• /
• public class MyFirstClass
• //public constants
• //attributes
• private boolean isSomething
• private int aCounter
• //methods
• public void doSomething()
• //code goes here

7
Examples (if)

• if (x y)
• //executes if true
• if (somethingIsTrue())
• doSomething()
• else
• doSomethingElse()

8
Example (for)

• int x0
• for (int i1 ilt10 i)
• //code to repeat ten times
• x x i

9
Example (while)

• int x0
• while (x lt 10)
• doSomething()
• x
• //loop forever
• while (true)

10
Common Sources of Error

• Mistakes in naming
• Wrong case, illegal names
• class name and source file name not the same
• Missing semi-colon
• Missing curly brackets
• Incorrect Loop checks
• Loop is too large/small, or occurs forever
• Testing equality
• Assignment with (single equals sign)
• Comparison with (two equals signs)

11
Overview

• Java Syntax
• Quick Overview
• Robocode
• How it works
• Writing Robots
• Anatomy of a Robot
• Practical Exercises

12
Anatomy of a Robot

• package yourname
• import robocode.
• /
• Description of Robot
• /
• public class MyRobot extends Robot
• /
• Description of run method
• /
• public void run()
• //the robots behaviour