Datatypes in Java

Data Types In Java

Data types are the types of data that can be stored inside variables. Java is a statically typed language, so all the variables must be declared before use.

Example

 int age = 21;
Info

Here age is variable, and int is a data type. int means it stores an integer value, i.e., numbers without a decimal point.

Data Types are categorized into:

  • Primitive Data Types: byte, short, int, long, char, boolean, double
  • Reference Data Types: String, Arrays, Classes

Primitive Data Types

Primitive data types are the data types that can be stored without the use of any other data types. It has no additional methods. They are:

Data Types Description
byte Stores whole numbers from -127 to 127.
short Stores whole numbers from -32,768 to 32,768.
int Stores whole numbers from -2,147,483,648 to 2,147,483,647.
long Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854.,775,807
boolean Stores either true or false.
char Stores single character from A-Z, a-z, and symbol.
float Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits.
double Stores fractional numbers. Sufficient for storing 15 decimal digits.

Example

public class Main {
    public static void main(String[] args) {
        // Declaring various data types.
        byte bNum = 127;
        short sNum = 32767;
        int myNum = 2147483647; // Mostly Used
        long lNum = 9223372036854775807L;
        float fNum = 3.14f;
        double dNum = 3.14; // Mostly Used
        boolean isMarried = true;
        char myCh = 'A';

        // Displaying Result
        System.out.println("The value of bNum is "+bNum);
        System.out.println("The value of sNum is "+sNum);
        System.out.println("The value of myNum is "+myNum);
        System.out.println("The value of lNum is "+lNum); 
        System.out.println("The value of fNum is "+fNum);
        System.out.println("The value of dNum is "+dNum);
        System.out.println("The value of isMarried is "+isMarried);
        System.out.println("The value of myCh is "+myCh);
    }
}
Show Output

Reference Data Types

Reference data type is a data type that is created by the programmer. It is a class, interface, or an array. It is created using the keyword new. It has additional methods. You will learn String, Arrays, and Classes later in this guide. It is also called reference type because it refers to an object.

Type Casting

Type casting is the process of converting one data type to another. It is also called type conversion. It is done to store a value of one data type into another data type. It is done in two ways:

  • Implicit Type Casting: It is done automatically when the value is stored in a variable of a larger data type. For example, if you store an int value into a long variable, it will be done automatically.

  • Explicit Type Casting: It is done manually by the programmer. For example, if you store a long value into an int variable, it will give an error. So, you have to convert it manually.

Example: Convert int to long

In this example, we will convert an int value to long.

public class Main {
    public static void main(String[] args) {
        int myInt = 9;
        long myLong = myInt; // Automatic casting: int to long
        System.out.println("Value of myInt is: "+myInt);      // Outputs 9
        System.out.println("Value of myLong is: "+myLong);     // Outputs 9
    }
}
Show Output

Example: Convert long to int

In this example, we will convert a long value to int.

public class Main {
    public static void main(String[] args) {
        long myLong = 9;
        int myInt = (int) myLong; // Manual casting: long to int
        System.out.println("Value of myLong: "+myLong);     // Outputs 9
        System.out.println("Value of myInt: "+ myInt);      // Outputs 9
    }
}
Show Output

Interview Questions

  • What is type casting in Java? Why is it needed?
  • What is the difference between a primitive and a reference type?
  • Why Selection of correct type is important?
  • Is the declaration of a below is correct? Explain.
short salary = 100000;