Data Types in Java

Introduction to Data Types in Java

A data type is a keyword; it describes the type of data. Data types are having different sizes and values, and the values are stored in a variable. Java data types are broadly categorized into Primitive data types and Non-primitive data types. Primitive data types are char, byte, short, int, long, float, double, boolean. The non-primitive data type is String.

How Data Types come into the Picture?

Java allows 3 types of constants.

• Character constant
• Numeric constant
• Boolean constant

1. Character constant

Character constants are alphabets, words, special symbols and digits (0-9).

In Java, 2 types of character constants are there.

• Single character constant
• String constant

a. Single character constant: Single character constant is defined as”single letter surrounded in single quotes (‘ ’)”. Data type is char.

Example: ‘4’, ‘a’,’ ’(empty space) etc.

Limitation: We should not declare more than one character in single quotes; if we do so java compiler complains about it.

Example: ‘12’ is the wrong declaration.

b. String constant: String constants are a “group of letters enclosed in double quotes”. The data type is a string.

Example: ”Amardeep”, “!@#$”, “1234”,”30-Mar-1995” etc

2. Numeric constant

All numbers in java are said to numeric constants only.

There are 2 types of numeric constants.

• Integer numeric constant
• Decimal/real/floating-point numeric constant

a. Integer numeric constant: A number without fractional part is called an Integer numeric constant. The data type is int.

Example: -1, -2, -5, 6, 7, 8, 0 etc.

b. Decimal/real/floating-point numeric constant: A number with fractional part is called a decimal or floating numeric constant. Data types are float and double.

Example: -1.23, 1.23, 5.67, 7.0, 5.28 etc.

3. Boolean constant

Java stores Boolean values as true, or Data type is boolean.

Example: true, false

Data Summary

Given below is the data summary:

• Single character constant
• String constant
• Integer constant
• Decimal constant
• Boolean constant

Java Data Types

Java data types are categorized into 2 types:

1. Unsigned

There is no sign bit allocation for memory means we don’t have any positive or negative value for characters.

Examples: a. Characters

2. Signed

There is a sign bit allocation for memory means integers and decimal numbers have positive and negative values. So every first bit allotted for -(minus) or + (plus) sign bit and rest of the bits are allotted for number. For the negative number, the sign bit is 1, and the positive number sign bit is 0.

Sign Bit-1

2

3

4

5

……

……

……

……

……

Examples:

• Integer
• Decimal
• String

1. Integer classification

Integer again is classified into 4 data types.

• byte: byte has 1-byte memory. 1 byte has 8 bits. As we have seen, 1^st bit is for the sign bit, and the rest 7 bits are for the number. Therefore byte size in java 2^-7 to (2^7)-1 means -128 to 127.
• short: short has 2 bytes memory. 2 bytes have 16 bits. As we have seen, 1^st bit is for the sign bit, and the rest 15 bits are for the number. Therefore the short size in java 2^-15 to (2^15)-1.
• int: int has 4 bytes memory. 4 bytes have 32 bits. As we have seen, 1^st bit is for the sign bit, and the rest 31 bits are for the number. Therefore int size in java 2^-31 to (2^31)-1.
• long: long has 8 bytes memory. 8 bytes have 64 bits. As we have seen, 1^st bit is for the sign bit, and the rest 63 bits are for the number. Therefore the long size in java 2^-63 to (2^63)-1.

2. Decimal classification

Decimal again is classified into 2 data types.

• float: float has 4 bytes memory. 4 bytes have 32 bits. As we have seen, 1^st bit is for the sign bit, and the rest 31 bits are for the number. float size in java 3.4E^-38 to 3.4E^38.
• double: double has 8 bytes memory. 8 bytes have 64 bits. As we have seen, 1^st bit is for the sign bit, and the rest 63 bits are for the number. double size in java 1.7E^-308 to 1.7E^308.

3. String

A string is also an unsigned data type in java.

Data types table:

S.No	Data	Data Type	Signed/Unsigned	Size	Ranges
1	Single character constant	char	Unsigned	2 bytes	0 to 65535
2	Integer constant	byte	Signed	1 byte	2^-7 to (2^7)-1
		short	Signed	2 bytes	2^-15 to (2^15)-1
		int	Signed	4 bytes	2^-31 to (2^31)-1
		long	Signed	8 bytes	2^-63 to (2^63)-1
3	Decimal constant	float	Signed	4 bytes	3.4E^-38 to 3.4E^38
		double	Signed	8 bytes	1.7E^-308 to 1.7E^308
4	Boolean constant	boolean	Signed	JVM dependent	true/false
5	String constant	String	Signed	JVM dependent	JVM dependent

Classification of Java Data Types

Given below is the classification of Java Data Types:

• Primitive data type
• Reference data type

1. Primitive data type

Among 9 data types, 8 are primitive data types.

• char
• byte
• short
• int
• long
• float
• double
• Boolean

2. Reference data type

Among 9 data type’s only one reference type is there.

• String: It is also called class type.

Why Java char has 2 Bytes, and other Programming Languages have 1 Byte Memory?

• Java has designed by using UTF-16 ( Unicode Transformed Format).
• Originally the char data type used for representing 16 bit Unicode.
• So Java char has 2 bytes.

How does Data Types work in Java?

Based on the type assigned to a variable, the corresponding operation performs.

Syntax: Primitive data types

1. char

char variableName=value;

2. byte

byte variableName=value;

3. short

short variableName=value;

4. int

int varibaleName=value;

5. long

long varibaleName=value;

6. float

float varibaleName=value;

7. double

double varibaleName=value;

8. boolean

booleanvaribaleName=value;

Syntax: Reference data type

1. String

String variableName=value;

Default values for data types are given below:

Examples of Data Types in Java

Given below are the examples mentioned:

Example #1: Character values

Code:

public class Characters
{
//char global declaration
static char global;
public static void main(String[] args) {
//char local decalration
char a='a';
char b='b';
char c='c';
char d='d';
System.out.println("Character with char data type");
System.out.println(global);//gives you default value with empty means '\u0000'
System.out.println(a);
System.out.println(b);
System.out.println(c);
System.out.println(d);
}
}

Output:

Example #2: String

Code:

public class StringDemo {
static String globalString;
public static void main(String[] args) {
String name1="Amardeep";
String specialChars="@#$%^";
System.out.println("Strings with String data type");
System.out.println(globalString);
System.out.println(name1);
System.out.println(specialChars);
}
}

Output:

Example #3: Integer data type

Code:

public class IntegerDataTypes {
static byte globalByte;
static short globalShort;
static int globalInt;
static long globalLong;
public static void main(String[] args) {
byte b=-128;
short s=23456;
int i=432198;
long l=34534534L;//we can specify long value by suffix L
System.out.println("Default Integer values byte :"+globalByte+" short :"+globalShort+" int :"+globalInt+" long :"+globalLong);
System.out.println("Integer values byte :"+b+" short :"+s+" int :"+i+" long :"+l);
}
}

Output:

Example #4: Decimal data type

Code:

public class DecimalDataType {
static float globalFloat;
static double globalDouble;
public static void main(String[] args) {
float f=2538.23f;//we can specify float value by suffix f
double d=2358.36d;//we can specify double value by suffix d
System.out.println("Default Decimal value float :"+globalFloat+" double :"+globalDouble);
System.out.println("Decimal values float :"+f+" double :"+d);
}
}

Output:

Example #5: Boolean data type

Code:

public class BooleanDataType {
static booleanglobalBoolean;
public static void main(String[] args) {
boolean b=true;
System.out.println("Default booleanvalue :"+globalBoolean);
System.out.println("Boolean value:"+b);
}
}

Output:

Conclusion

Data Types in Java are primitive and reference types char, byte, short, int, long, float, double, boolean, and String, respectively. Data types decide the behavior of data.

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