Computer Programming: Java - Week 01 Notes

Introduction to Computer Programming with Java

Hardware vs. Software

• Hardware: Physical electronic devices.
  • Examples: phone, computer components.
• Software: Instructions that tell hardware what to do.
  • Examples: apps on a phone.

Integrated Development Environments (IDEs)

• Using an IDE to write software.
• Example IDE: Eclipse.
• Choice of IDE is flexible (NetBeans, Dr. Java, etc.).

Types of Programming Languages

• Low-Level Languages:
  • Directly understood by the computer.
  • Difficult to read and write.
  • Require many instructions for simple tasks.
• High-Level Languages:
  • Easier to read and write.
  • Fewer commands accomplish more.
  • Example: Java (System.out.println(“Hi”);)

Java Code Structure

• Java code is stored in files.
  • .java files: Contain the Java code you write.
  • .class files: Contain translated Java code that the computer understands.
• Java code is organized into projects.

Basic Java Program Structure

• All Java programs must follow a specific structure:

  public class ClassName {
      public static void main(String[ ] args) {
          // Your program goes here
      }
  }
  

• The class name should match the file name (without the .java extension).

  • Example: HelloWorld.java

Variables

• Definition: A named location in memory that stores a value.
• Analogy: Like 'x' in the function $f(x) = 2x + 4$.
  • If $f(x) = 2x + 4$, then to evaluate $f(1)$, we store 1 in 'x'.
• In Java, variables can hold numbers, words, and other types of data.
• Examples:
  • String myFirstVariable;
  • int mySecondVariable;

Variable Naming Conventions

• Good Examples:
  • age
  • firstName
  • numberOfClasses
  • hour
  • fred
• Bad Examples:
  • FirstName
  • firstname
  • VariablePractice.java

Common Errors with Variables

1. String firstName = Joe;
   • Error: Missing quotes around Joe. Should be `String firstName =