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, 1st 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, 1st 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, 1st 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, 1st 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, 1st 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, 1st 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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This is a guide to Data Types in Java. Here we discuss the introduction to Data Types in Java, classification of data types, how does these work, and examples. You may also have a look at the following articles to learn more –
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