Chapter 1 Introduction

Chapter Scope

• Introduce the Java programming language

• Program compilation and execution

• Problem solving in general

• The software development process

• Overview of object-oriented principles

Java Overview

• A computer consists of hardware (physical components) and software (programs and data).

• Hardware: The physical components doing the computing.

• Software: Instructions (programs) that run on hardware.

• Programs, also known as applications, execute serially by the hardware.

Programming Languages

• A programming language defines the lexicon and syntax for writing programs.

• Rules govern the arrangement of words and symbols to form valid statements.

• Java programming language was created by Sun Microsystems, Inc. and released in 1995.

Program Structure in Java

• A Java program is composed of:

  • One or more classes.

  • Each class contains one or more methods.

  • Each method holds program statements.

• Every Java application includes a main method.

Sample Java Program Structure

• **Example Code:

public class Lincoln {
   public static void main(String[] args) {
       System.out.println("A quote by Abraham Lincoln:");
       System.out.println("Whatever you are, be a good one.");
   }
}

• Comments can be included almost anywhere within the program.

Java Program Components

• Program Header: public class MyProgram {}

  • Defines the class.

• Main Method Header: public static void main(String[] args) {}

  • Defines the entry point.

• Comments: Explain purposes and processing within the code:

  • Line Comments (//)

  • Block Comments (/*...*/)

  • Javadoc Comments (/**...*/)

Identifiers

• Identifiers are names given by programmers in code.

• Can include letters, digits, underscores (_), and dollar signs ($), but cannot start with a digit.

• Java is case-sensitive: Total, total, and TOTAL are different.

• Naming conventions include:

  • Title case for class names: Lincoln

  • Upper case for constants: MAXIMUM

Reserved Words

• Reserved words are predefined words in Java that have specific functions and cannot be used as identifiers.

Whitespace

• Whitespace (spaces, tabs, and blank lines) separates symbols and names.

• Extra whitespace is ignored, but good formatting enhances readability.

Program Development Basics

• Includes activities like:

  • Writing the program in a programming language.

  • Translating it into executable form.

  • Investigating/fixing errors.

• Software tools assist in this development process.

Language Levels

• Four programming language levels exist:

  • Machine Language

  • Assembly Language

  • High-Level Language

  • Fourth-Generation Language

• Machine languages are CPU-specific.

Compilation Process

• Programs must be translated into machine language to execute.

• Compiler: Software translating source code into machine language.

• Java compiles to bytecode, which is platform-independent.

Java Execution Flow

• Java compiler translates source code into bytecode, later interpreted to machine language.

• Java programs are thus architecture-neutral due to this unique compilation-execution method.

Development Environments

• A development environment comprises all tools like compilers and interpreters needed to create programs.

• Integrated Development Environments (IDEs) combine tools (e.g., JDK, Eclipse, NetBeans).

Syntax and Semantics

• Syntax defines the language structure; semantics define statement meaning.

• A syntactically correct program may still have logical errors.

Error Types

1. Syntax Errors: Caught at compile-time.

2. Run-Time Errors: Occur during execution (e.g., division by zero).

3. Logical Errors: Produce incorrect results despite successful execution.

Problem Solving Steps

• Multiple activities involved when solving a problem:

  • Understand the problem.

  • Design a solution.

  • Implement and test the solution.

• Activities are interlinked and not strictly linear.

Object-Oriented Programming

• Java is object-oriented, using objects to represent real-world entities.

• Example: An employee object could manage its own data and behavior.

Objects and Classes

• Objects have:

  • State: Characteristics (e.g., bank account number).

  • Behaviors: Actions (e.g., deposits, withdrawals).

• Objects are defined by classes, which serve as blueprints.

• A class encapsulates data and behaviors, protecting its internal state.

Class Hierarchies

• Classes can inherit characteristics from other classes, allowing for organized structures that model real-world relationships.