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Data types in java with example

Data type is used to specify the type of data that variable can hold. A variable’s data type determines what operations can be carried out on the variable’s data, as well as the amount of memory needed to hold the data.

Java has 3 types of data types

  1. Primitive Types: byte, short, int, long, float, double, char and boolean 

  2. Derived Types: Arrays 

  3. User Defined Types: Class, subclass, abstract class, interface, enumerations and annotations 

Integers

This group includes byte, short, int, and long, which are for whole-valued signed numbers. Java does not support unsigned, positive-only integers. Many other computer languages support both signed and unsigned integers. All four byte, short, int, and long are signed. If a large value is used then we use long data type, but for such long values need append “L” at last

public class IntegerDemo {

        public static void main(String[] args) {

                long y = 12345678987654321L; // notice the “L”

        }

}

An interesting note about Java is that it performs integer arithmetic at the int level. Octal numbers must start with 0. Hexadecimal numbers must start with 0x or 0X.

Floating-Point Types

Float values are known as real numbers. float is single- precision number and double is double-precision number. Floating-point literals are treated as a double value by default .Hence if we assign any floating point literal to a variable, value will be assigned as double. . Thus if we want to assign  floating-point literals as  single- precision we need to append   “ F” to the value at last. Assigning a value to float data type without appending “F” gives an error. Because Floating-point literals are treated as double value by default which is double-precision and float is single- precision. Hence single- precision variable cannot store single- precision value, possible loss of precision Error comes.

public class FloatDemo {

        public static void main(String [] args) {

                double pi = 3.14159;

                float f = 2.7F;

                System.out.println("pi = " + pi);

                System.out.println("f = " + f);

                int n = 15, d = 4;

                f = n/d;

                System.out.println("15/4 = " + f);

                int radius = 10;

                double area = pi * radius * radius;

                System.out.println("area = " + area);

        }

}

 

Boolean Data Type

boolean is a built-in data type in java used to represent Boolean values. A variable of type boolean can be either true or false. Note that true and false are special literals in Java.

public class BooleanDemo {

        public static void main(String [] args) {

                boolean t = true;

                System.out.println("t is " + t);

                int x = 10;

                boolean y = (x > 15);

                System.out.println("y is " + y);

                // y = x; // Does not compile!

        }

}

Char Data Type

Single quotes are used to denote a character literal.

class CharDemo {

        public static void main(String args[]) {

                char ch1;

                ch1 = 'A';

                System.out.println("ch1 contains " + ch1);

                ch1++; // increment ch1

                System.out.println("ch1 is now " + ch1);

        }

}

 

Output:

 

ch1 contains A

ch1 is now B

 

In this Program if ch1=M, then ch1++ will be N, if ch1=I, then ch1++ will be J.

class CharDemo {

        public static void main(String args[]) {

                char ch1 = 65;

                System.out.println(ch1);

        }

}

This program prints A, which is the UNICODE equivalent of 65.       

Size and range of data types

Type

Data Type

Size (bits)

Minimum Value

Maximum Value

Default Value

Integers

long

64

-2(64-1)

2(64-1)-1

0

Int

32

-2(32-1)

2(32-1)-1

0

short

16

-2(16-1)

2(16-1)-1

0

byte

8

-2(8-1)

2(8-1)

0

Floating-Point

double

64

4.9e–324

1.8e+308

0.0

float

32

1.4e–045

3.4e+038

0.0

char

char

16

\u0000

uFFFF

Space

boolean

boolean

n/a

true or false

 

false

Array

Declaring an array

Use any of the below syntax:

dataType[] nameOfArray;

dataType [] nameOfArray;

dataType []nameOfArray;       

dataType nameOfArray[];

dataType nameOfArray [];

Example :

int[] arr;

int [] arr;

int []arr;

int arr[];

int arr [];

Instantiating array

nameOfArray = new dataType[size];

arr = new int[10];

Initializing array

Values should match with the data type of array

nameOfArray[index] = value;

int[0] = 50; int[1] = 100;

The below assignment is not possible due to data type mismatch

int[0] = true; int[1] = ‘A’;

Declaring and instantiating  array

dataType[] nameOfArray = new dataType[size];

dataType [] nameOfArray = new dataType[size];

dataType []nameOfArray = new dataType[size];

dataType nameOfArray[] = new dataType[size];

dataType nameOfArray [] = new dataType[size];

int[] arr1 = new int[10];

int [] arr2 = new int[10];

int []arr3 = new int[10];

int arr4[] = new int[10];

int arr5 [] = new int[10];

 

Declaring, instantiating  and initializing array

dataType[] nameOfArray = {value1, value2…};

dataType [] nameOfArray = {value1, value2…};

dataType []nameOfArray = {value1, value2…};

dataType nameOfArray[] = {value1, value2…};

dataType nameOfArray [] = {value1, value2…};

int[] arr1 = {1, 2, 3};       

int [] arr2 = {1, 1, 1};       

int []arr3 = {4, 5, 3};

int arr4[] = {4, 4, 6};

int arr5 [] = {1, 8, 3};

 

 

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