Java Data Types

Why Java is a strongly typed language?

• In Java, every variable has a type, every expression has a type, and every type is strictly defined.
• Type compatibility is checked in java for all assignments, whether explicit or via parameter passing in method calls.
• Java compiler checks all expressions and parameters in the code to ensure that types are compatible. Java compiler throws the errors if any type mismatches.

What are the data types?

• Simple types of data in java: byte, short, int, long, char, float, double and boolean.
• Four primary groups in data types:
  • Integers: This group includes byte, short, int and long types. Values for this four types are signed numbers, both positive and negative values. Java does not support unsigned positive only integers.

    Data type	Length (in bits)	Range	Default Value
    byte	8	-128 to 127	0
    short	16	-32,768 to 32,767	0
    int	32	-2,147,483,648 to 2,147,483,647	0
    long	64	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	0L

    Java program for defining integers

    class IntegersTest {                                                            
     public static void main(String args[]) {                                       
      byte a = 10;                                                                  
      short b = 500;                                                                
      int c = 350000;
      // Long integer must be initialized using L in the end.                                                              
      long d = 22000000000L;                                                        
      System.out.println("byte a: " + a);                                           
      System.out.println("short b: " + b);                                          
      System.out.println("int c: " + c);                                            
      System.out.println("long d: " + d);                                           
     }                                                                              
    } 
    

    Output:

    byte a: 10
    short b: 500
    int c: 350000
    long d: 22000000000
    

    When assigning long value, need to use L with the long integer value. Otherwise compiler throws error: integer number too large.
  • Floating-point numbers: This group includes float and double. This is also known as real numbers, are used for evaluating expressions that require fractional precision. Java implements the standard (IEEE-754) set of floating point types and operations.

    Data type	Length (in bits)	Range	Default Value
    float	32	4.9e-324 to 1.8e+308	0.0f
    double	64	1.4e-045 to 3.4e+038	0.0d

    Java program to define float and double numbers

    class FloatingNumbersTest {                                                     
     public static void main(String args[]) {                                       
      float radius = 12.5f;                                                         
      float pi = 3.14f;                                                             
      double area;                                                                  
      area = (pi * radius  * radius);                                               
      System.out.println("area of circle is: " + area);                             
     }                                                                              
    }  
    

    Output:

    area of circle is: 490.625
    

  • Characters: This group includes char. values are character set like letters and numbers. In java, uses unicode (which is 16bit type) to represent the characters. Unicode defines a fully international character set that can represent all of the characters found in all human languages. Character default value is '\u0000'.

    What are the character escape sequences in java?

    Escape Sequence	Description
    \n	New line( or line feed)
    \r	Carriage return
    \f	Form feed
    \t	Tab
    \b	Backspace
    \'	Single quote
    \"	Double quote
    \\	Backslash
    \ddd	Octal character (ddd)
    \uxxxx	Hexadecimal unicode character(xxxx)

    Java program to define characters

    class CharacterTest {                                                           
     public static void main(String args[]) {                                       
      char char1, char2;                                                            
      
      //Character unicode for 'L'                                                                              
      char1 = 76;                                                                   
      char2 = 'J';                                                                  
                                                                                    
      System.out.println("char1: " + char1);                                        
      System.out.println("char2: " + char2);                                        
     }                                                                              
    }   
    

    Output:

    char1: L
    char2: J
    

  • Boolean: This group includes boolean. values are either true or false and default value is false. This is returned by all relational operators.

    Java program to define boolean variable
    class BooleanTest {                                                             
     public static void main(String args[]) {                                       
      boolean a = true;                                                             
      boolean b = false;                                                            
                                                                                    
      System.out.println("boolean a: " + a);                                        
      System.out.println("boolean b: " + b); 
      // Bitwise AND operator, result is true if both variables are true.                                       
      System.out.println("boolean (a & b): " + (a & b));  
      //Bitwise OR operator, result is true if either one variable is true.
      System.out.println("boolean (a | b): " + (a | b));                             
     }                                                                              
    }  
    

    Output:

    boolean a: true
    boolean b: false
    boolean (a & b): false
    boolean (a | b): true