Variables

In Java, variables are containers that store data values. They have a data type and a name. Here are some common types of variables in Java along with examples:

Primitive Data Types:

These are basic data types representing single values.

Examples:

• int age = 25; // Integer variable
• double salary = 55000.50; // Double variable
• char grade = 'A'; // Character variable
• boolean isStudent = true; // Boolean variable

Reference Data Types:

These variables refer to objects. They don't store the actual data but the memory address of the data.

Examples:

• String name = "John"; // String is a reference data type

Arrays:

Arrays are used to store multiple values of the same type in a single variable.

Examples:

• int[] numbers = {10, 20, 30, 40, 50}; // Array of integers
• String[] colors = {"Red", "Green", "Blue"}; // Array of strings

Constants:

Constants are variables whose values cannot be changed once assigned.

Examples:

• final int MAX_VALUE = 100; // Constant variable

Local Variables:

Variables declared inside a method or block of code.

Examples:

void exampleMethod() {

    int localVar = 5; // Local variable

}

Instance Variables (Non-static Fields):

Variables declared within a class but outside any method, constructor, or block.

Examples:

public class MyClass {

    int instanceVar = 10; // Instance variable

}

Static Variables (Class Variables):

Variables declared with the static keyword, shared by all instances of a class.

Examples:

public class MyClass {

    static int staticVar = 20; // Static variable

}

Enum Constants:

Enumerations define a fixed set of constants.

Examples:

public enum Day {

    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY

}

Implicit Type Conversion:

Java automatically converts smaller data types to larger ones.

Examples:

int intValue = 42;

double doubleValue = intValue; // Implicit casting

Explicit Type Conversion (Casting):

When converting from a larger data type to a smaller one, explicit casting is required.

Examples:

double bigValue = 123.45;

int intValue = (int) bigValue; // Explicit casting

These examples cover a range of variable types and scenarios in Java. Understanding these concepts is crucial for writing effective and readable Java code.