Introduction

In our previous discussion, we explored Java’s ecosystem, set up our development environment, and executed our first Java program. Now, we move forward with an essential concept – data types and variables, which form the foundation of data storage and manipulation in Java.

Data Types

A data type defines the nature of data stored in a variable, determining its memory allocation and the operations that can be performed on it. Java categorizes data types into two:

1. Primitive Data Types

These are the fundamental, built-in types that store values directly in memory. Java provides eight primitive data types, namely:

• Integer Types: byte (1 byte), short (2 bytes), int (4 bytes), long (8 bytes)

• Floating-Point Types: float (4 bytes), double (8 bytes)

• Character Type: char (2 bytes, stores a single character)

• Boolean Type: boolean (1 bit, stores true or false)

2. Non-Primitive Data Types

These types store references (memory addresses) rather than actual values. They include:

• Strings (String): A sequence of characters

• Arrays (int[], String[], etc.): Collections of values of the same type

• Classes & Objects: User-defined data structures

• Interfaces: Abstract types for defining contracts

• Enumerations (enum): A special data type for fixed sets of constants

Variables in Java

A variable is a named memory location that holds a data value, allowing the program to store and manipulate information.

Declaring and Initializing Variables

In Java, every variable must be declared with a specific data type before use. Once declared, its type cannot be changed within the program. If a different type is needed, a new variable must be created.

public class DataTypesAndVariables {
    public static void main(String[] args) {

        // Variable declaration and initialization
        int age = 25;  // Integer variable
        double price = 19.99;  // Floating-point variable
        char grade = 'A';  // Character variable
        boolean isJavaFun = true;  // Boolean variable

        // String and array examples
        String message = "To Java or not to Java, that's the statement!";
        int[] numbers = {1, 2, 3, 4, 5};
    }
}

From the above code snippet, int is the data type, age is the variable and 25 is the value stored in the variable.

Conclusion

Understanding data types and variables is crucial for writing efficient Java programs. Primitive types store values directly in memory, while non-primitive types store addresses. Variables serve as essential storage units, enabling data manipulation and computation. Mastering these concepts sets the stage for more advanced programming topics such as control flow, functions, and object-oriented programming.