Variables & Data Types in Java

Variables are containers for storing data values

In Java, there are different types of variables

  • String: Stores text
  • int and long: Stores integers
  • float and double: Stores floating point numbers
  • char: Stores single characters
  • boolean: Stores values with two states: true or false

String Data Type

The String data type stores a sequence or array of characters.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		String fullName = "Kevin";
		System.out.println("full name: " + fullName);

		String email = "octopuscodes@gmail.com";
		System.out.println("email: " + email);
	}
}
Output:
full name: Kevin
email: octopuscodes@gmail.com
 

Int Data Type

The int data type stores integers (whole numbers), without decimals.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		int age = 20;
		System.out.println("age: " + age);

		int quantity = 15;
		System.out.println("quantity: " + quantity);
	}

}
Output:
age: 20
quantity: 15
 

Long Data Type

The long data type is used when a wider range than int data type is needed.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		long creditCardNumber = 5467123456321234L;
		System.out.println("creditCardNumber: " + creditCardNumber);

		long quantity = 10000;
		System.out.println("quantity: " + quantity);
	}

}
Output:
creditCardNumber: 5467123456321234
quantity: 10000

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Float Data Type

The float data type stores floating point numbers.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		float pi = 3.14f;
		System.out.println("pi: " + pi);
		
		float scores = 7.8f;
		System.out.println("scores: " + scores);

		float area = 13456.1574f;
		System.out.println("area: " + String.format("%.2f", area));
	}

}
Output:
pi: 3.14
scores: 7.8
area: 13456.16
 

Double Data Type

The double data type is similar to float. The difference between the two is that is double twice the float in the case of decimal precision.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		double price = 123.56;
		System.out.println("price: " + price);

		double perimeter = 56.7234;
		System.out.println("perimeter: " + perimeter);

		double area = 12456.1574;
		System.out.println("area: " + String.format("%.2f", area));
	}

}
Output:
price: 123.56
perimeter: 56.7234
area: 12456.16
 

Char Data Type

The char data type stores a single character/letter or ASCII values.

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		char key = 'H';
		System.out.println("key: " + key);

		char ch = 97;
		System.out.println("ch: " + ch);
	}

}
Output:
key: H
ch: a
 

Boolean Data Type

The boolean data type stores values with two states: true or false

Example:
package octopuscodes.com.demo;

public class Demo {

	public static void main(String[] args) {
		boolean status = true;
		System.out.println("status: " + status);

		boolean active = false;
		System.out.println("active: " + active);
	}

}
Output:
status: true
active: false