Java Programming Data Types Variables And Operators Complete Guide

1. Data Types in Java

Data types define the type of data a variable can hold and the operations that can be performed on it. Java is a statically typed language, meaning you must declare the data type of a variable before using it.

Primitive Data Types (Built-in)

• byte - 1 byte, ranges from -128 to 127
• short - 2 bytes, ranges from -32,768 to 32,767
• int - 4 bytes, ranges from -2,147,483,648 to 2,147,483,647
• long - 8 bytes, ranges from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
• float - 4 bytes, single-precision, 6 to 7 decimal digits
• double - 8 bytes, double-precision, 15 to 16 decimal digits
• char - 2 bytes, single 16-bit Unicode character
• boolean - 1 bit, true or false

Reference Data Types (Non-Primitive)

• String - a sequence of characters
• Array - a collection of similar type of elements
• Object - instances of classes
• Class - blueprint from which individual objects are created
• Interface - a contract for classes to implement

Example: Declaring Variables with Primitive Data Types

public class DataTypeExample {
    public static void main(String[] args) {
        // Declaring variables of various primitive data types
        byte myByte = 100;
        short myShort = 5000;
        int myInt = 100000;
        long myLong = 1500000000L;  // Use 'L' for long literals
        float myFloat = 3.14f;      // Use 'f' for float literals
        double myDouble = 3.14159;
        char myChar = 'A';
        boolean myBoolean = true;

        // Printing the values of the variables
        System.out.println("Byte: " + myByte);
        System.out.println("Short: " + myShort);
        System.out.println("Integer: " + myInt);
        System.out.println("Long: " + myLong);
        System.out.println("Float: " + myFloat);
        System.out.println("Double: " + myDouble);
        System.out.println("Character: " + myChar);
        System.out.println("Boolean: " + myBoolean);
    }
}

Output:

Byte: 100
Short: 5000
Integer: 100000
Long: 1500000000
Float: 3.14
Double: 3.14159
Character: A
Boolean: true

2. Variables in Java

A variable is a container used to store data values. It acts as a reference to the memory location where data values are stored. You can declare variables before using them, and initialize them with values.

Syntax:

dataType variableName = value;

Example: Declaring and Initializing Variables

public class VariableExample {
    public static void main(String[] args) {
        // Declaring and initializing variables
        int studentAge = 20;
        String studentName = "John Doe";
        double studentGPA = 3.85;
        boolean isEnrolled = true;

        // Printing the values of the variables
        System.out.println("Student Name: " + studentName);
        System.out.println("Student Age: " + studentAge);
        System.out.println("Student GPA: " + studentGPA);
        System.out.println("Is Enrolled: " + isEnrolled);
    }
}

Output:

Student Name: John Doe
Student Age: 20
Student GPA: 3.85
Is Enrolled: true

3. Operators in Java

Operators are symbols used to perform operations on variables and values.

Types of Operators:

• Arithmetic Operators: +, -, *, /, %
• Assignment Operators: =, +=, -=, *=, /=, %=
• Comparison Operators: ==, !=, >, <, >=, <=
• Logical Operators: && (and), || (or), ! (not)
• Bitwise Operators: &, |, ^, ~, <<, >>, >>>
• Increment/Decrement Operators: ++, --

Example: Using Arithmetic and Assignment Operators

public class OperatorExample {
    public static void main(String[] args) {
        // Declaring and initializing variables
        int a = 10;
        int b = 5;
        int result;

        // Using arithmetic operators
        result = a + b;
        System.out.println("Addition: " + result);

        result = a - b;
        System.out.println("Subtraction: " + result);

        result = a * b;
        System.out.println("Multiplication: " + result);

        result = a / b;
        System.out.println("Division: " + result);

        result = a % b;
        System.out.println("Modulus: " + result);

        // Using assignment operators
        a += b;  // a = a + b
        System.out.println("a after a += b: " + a);

        a -= b;  // a = a - b
        System.out.println("a after a -= b: " + a);

        a *= b;  // a = a * b
        System.out.println("a after a *= b: " + a);

        a /= b;  // a = a / b
        System.out.println("a after a /= b: " + a);

        a %= b;  // a = a % b
        System.out.println("a after a %= b: " + a);
    }
}

Output:

Addition: 15
Subtraction: 5
Multiplication: 50
Division: 2
Modulus: 0
a after a += b: 15
a after a -= b: 10
a after a *= b: 50
a after a /= b: 10
a after a %= b: 0

Example: Using Comparison and Logical Operators

public class LogicalComparisonExample {
    public static void main(String[] args) {
        int x = 10;
        int y = 5;

        // Comparison operators
        boolean isEqual = x == y;
        System.out.println("x == y: " + isEqual);

        boolean isNotEqual = x != y;
        System.out.println("x != y: " + isNotEqual);

        boolean isGreaterThan = x > y;
        System.out.println("x > y: " + isGreaterThan);

        boolean isLessThan = x < y;
        System.out.println("x < y: " + isLessThan);

        boolean isGreaterThanOrEqual = x >= y;
        System.out.println("x >= y: " + isGreaterThanOrEqual);

        boolean isLessThanOrEqual = x <= y;
        System.out.println("x <= y: " + isLessThanOrEqual);

        // Logical operators
        boolean andResult = isGreaterThan && isLessThan;
        System.out.println("x > y && x < y: " + andResult);

        boolean orResult = isGreaterThan || isLessThan;
        System.out.println("x > y || x < y: " + orResult);

        boolean notResult = !isGreaterThan;
        System.out.println("!isGreaterThan: " + notResult);
    }
}

Output: