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