Data Types in Java, Primitive Data Types, Non-primitive Data Types, Java Strings, Java Numbers, Java Characters, and Java Boolean Data Type.
Java Data Types
What is Data Type?
Data Type is a classification of the type of data that a Variable or Constant or Method can hold in computer programming
Example:
Character, Number, Number with decimal values, Logical data, String, Date, Currency etc…
Note: Java supports explicit declaration of Data Types.
(We need to specify the Data Type before declaring Variables, Constants, and methods…)
Chatcter (char)
chat s=’Z’;
Number (byte, short, int, long, float, double)
String
String a= “X”;
String b=”Selenium”,
String c=”Automated Testing using Selenium”,
Logical data (boolean),
Date
etc,
Syntax:
a. Variables
dataType variableName;
Or
dataType variableName = value;
Or
dataType variable1Name, variable2Name, variable3Name;
or
dataType variable1Name=value, variable2Name= value, variable3Name=value;
Example:
int a;
a=10;
int b=100;
int c, d, e;
c=30; d=40; e=50;
int f=60, g=70, h=80;
b). Constants
Note: Variables and Constants are for holding the data, Variables may vary, but constants never change
int a;
a=100;//Correct for Variable
.
.
.
.
a=30; //Correct for Variable
……………….
final int b;
b=200; //Incorrect
final int c =300;//Correct
.
.
.
c=400; //Incorrect
c. Method with Return Value
public int add(){ //Return type is int (Non Static Method)
.
.
return…;
}
……………….
public static int multiply(){ //Return type is int (Static Method)
.
.
return…;
}
……………….
public void sub(){ //No return type (Non Static Method)
.
.
}
……………….
public static void divison(){ //No return type (Static Method)
.
.
}
Two Categories of Data Types in Java
1) Primitive Data Types
2) Non-primitive data Types
1. Primitive Data Types
a) Integer Data Types
i) byte (8 bits)
- Minimum value is -128 (-2^7),
- Maximum value is 127 (inclusive)(2^7 -1)
- Default value is 0
Example:
byte a=100;
int x=100;
byte b=-129; //Out of Range
byte c=127;
byte d=128;//Out of Range
ii) short (16 bits)
- Minimum value is -32,768 (-2^15)
- Maximum value is 32,767 (inclusive) (2^15 -1)
- Default value is 0.
Example:
short b=1000;
iii) int (32 bits)
- Minimum value is – 2,147,483,648 (-2^31)
- Maximum value is 2,147,483,647(inclusive) (2^31 -1)
- The default value is 0
Example:
int a=1;
int b=1000;
int c= 100000000;
long d=9878787878l;//Out of Range
System.out.println(d);
iv) long (64 bits)
- Minimum value is -9,223,372,036,854,775,808(-2^63)
- Maximum value is 9,223,372,036,854,775,807 (inclusive)(2^63 -1)
- Default value is 0L
Example:
long x=1000;
long y=999999999;
long z=3333333333l;
b) Relational Data Types (Numbers with Decimal Places)
v) float (32 bits)
float x = 10.23f;
vi) double (64 bits)
double y = 1234.5678765;
c) Character Data Type
vii) character
char z = ‘A’;
char s = ‘1’;
char r = ‘*’;
d) Conditional Data Type
viii) boolean
boolean k = true/false;
2. Non Primitive data types / Reference data types
Non Primitive data types in Java are Objects (String, Array etc…)
Example:
int a=100;
String b=”100″;
JavaExamples c = new JavaExamples();
……………….
123 – Integer Data Type
‘Y’ -Character
123.34 – float/double
“Selenium Testing” – String
“abc123*&^” – String
“123” – String
1 – Integer
‘1’ – Character
Converting Data / Data Conversion
Whenever we read data then the computer program considers that data as String type data, we need to convert the data in order to perform mathematical operations, Note: Generally we convert String type to Integer Type/ Relational type, we can’t convert Alpha bytes to numbers, etc…
String to Integer
String x=”100″
int num= Integer.parseInt(x);
String to Double
String y=”10.234″;
String num = Double.parseDouble(y);