Lecture 04: Demonstration - I

How to Set Up Your Java Programming Environment

Overview of Java Program Execution

• The session begins with a discussion on how to run Java programs and the necessary resources for effective Java programming.

• Emphasis is placed on properly configuring your machine, whether using a laptop or PC, to execute programs from the project directory.

Setting Up the Development Environment

• The speaker outlines steps for editing and executing programs, highlighting various stages involved in program execution.

• A demonstration is planned to illustrate setting up the environment suitable for Java programming, specifically mentioning the installation of JDK version 8.

Installation and Configuration Steps

• After installing JDK 8, users are instructed to check their program files directory where JDK has been installed.

• Users must set environment variables such as JAVA_HOME pointing to the JDK installation path (C:Program FilesJavajdk).

Path Configuration

• The importance of setting system paths is discussed; this includes adding JAVA_HOME/bin to ensure all Java tools are accessible.

• A new project directory named "Display1" is created for organizing all related code files.

Compiling and Running Programs

• Users can create their project directories anywhere on their machines. Once created, they can compile and execute their programs.

• Notepad++ is recommended as an excellent text editor for writing Java programs due to its user-friendly interface.

Writing Your First Java Program

• The speaker opens Notepad++ to demonstrate writing a simple Java program titled "FirstJavaProgram."

• Instructions are provided on saving the file correctly with a .java extension after typing out the program code.

Compiling Your Program

• After saving, users need to navigate to Command Prompt or Terminal based on their operating system for compilation.

• The command javac FirstJavaProgram.java is introduced as essential for compiling the written program.

How to Compile and Run Your First Java Program

Compiling the Java Program

• The class extension for a Java file is consistent with its name, e.g., FirstJavaProgram.class, indicating successful compilation.

• To run the program, use the command java FirstJavaProgram followed by the class name; this will execute the compiled bytecode.

• The program utilizes a single statement: System.out.println(), which outputs "Congratulations on your first Java program" upon execution.

Running and Troubleshooting

• The output confirms that the program runs successfully after compiling it using javac and executing it with java.

• If there’s a mismatch between the class file name (e.g., FirstJavaProgram1) and the saved file name (FirstJavaProgram.java), compilation will fail due to naming inconsistencies.

Compilation Success Criteria

• Successful compilation requires that both names match; otherwise, running commands will result in errors as no corresponding class file exists.

• It’s crucial to ensure that the class name matches exactly with what is defined in your source code for successful execution.

Creating Additional Programs: Hello World Example

Writing and Compiling HelloWorld Program

• A new simple program named HelloWorld.java is introduced, containing only one statement similar to previous examples.

• After saving as helloworld.java, compile it using javac. If successful, run it with java HelloWorld.

Output of HelloWorld Program

• The output displays "Hello, World", confirming that basic print functionality works correctly within Java programs.

Using Multiple Print Statements

Adding More Output Messages

• An additional message "Hi" is included alongside "Hello, World", demonstrating how multiple outputs can be printed sequentially.

Understanding System.out.println()

• The method allows printing various messages on screen. Each message can be separated or concatenated using operators like "+".

Defining Classes and Arrays in Java

Introduction to Class Definition

• Discussion shifts towards defining classes in Java. A new example called TestArray illustrates how elements are stored within an array structure.

Saving Class Files Correctly

Understanding Array Initialization and Looping in Java

Basics of Array Declaration

• The discussion begins with the declaration of an integer array using square brackets, indicating initialization and memory allocation.

• An example is provided where an array contains elements 10, 20, 30, 40, and 50, demonstrating how to store values at specific indices (0 to 4).

• The size of the declared array is confirmed to be 5, which corresponds to the number of elements it holds.

Looping Through Array Elements

• A loop starts from index 0 and continues while i is less than a.length(), which returns the size of the array.

• Inside the loop, each element of the array is printed one at a time using System.out.println().

• The difference between println() and print() is explained; println() adds a new line after printing while print() does not.

Calculating Average Value

• After printing all elements, a variable named 'sum' is introduced to calculate the total value of all elements in the array.

• Another variable 'average' is declared as a float type for storing average values calculated by dividing 'sum' by the number of elements.

• Finally, this average value is printed out using another call to System.out.println(), showcasing its functionality.

Program Execution Results

• Upon successful compilation and execution of the program named TestArray.java, results display all stored numbers followed by their sum and average.

• Modifications are suggested for better output formatting by adjusting print statements within loops for clearer presentation.

Enhancing Output Presentation

• Suggestions include adding spaces between printed numbers for improved readability on output screens.

• The importance of structuring print statements effectively within loops is emphasized for clarity in displaying results.

Introduction to Multi-Dimensional Arrays

Declaring a 3D Array

• Transitioning into multi-dimensional arrays, specifically a three-dimensional array named 'my3DArray', which requires careful declaration due to its complexity.

• Memory allocation involves specifying dimensions (3x4x5), representing pages (3), rows (4), and columns (5).

Nested Loops for Data Input

• To populate this three-dimensional structure efficiently, nested loops are utilized: an outer loop iterates through pages while inner loops handle rows and columns respectively.

3D Array Management in Java

Understanding 3D Arrays

• The outermost loop is designed to read a 3-dimensional structure, iterating through each 2-dimensional array within the 3D array.

• The statement indicates that values are stored as products of indices (i, j, k) in the 3D array, which initiates the process of populating the array.

• After compiling and running the program successfully using javac, it demonstrates how to display a 3D array's output effectively.

• The program aims to visualize a 2D plot from a 3D array by utilizing two dimensions for representation.

Steps for Displaying Elements

• The first step involves displaying elements from the first layer of the 2-dimensional view before moving on to subsequent layers.

• Each stage corresponds to different configurations of arrays; specifically, it highlights how many rows and columns exist at each level (4 rows and 5 columns).