Datatypes In Java

Primitive variables local variables will store in stack.
Datatypes defines how to store variables value in stack memory.

Java has eight primitive type.....

        DataType      Explanation
        
        byte          The memory size allocated to byte is 8 bits.
                      range from -128 to 127 (total of 256 numbers)
                      useful when working with a stream of data from a network or file. 
                         Ex. uploading large file on server byte by byte.
                      declaration -   byte b, c;
                      
        int           Range from -2,147,483,648 to 2,147,483,647
                      Represents a total of 4,294,967,296 numbers.        
                      A 32-bit (4-byte) integer value
                      
        short         Memory size allocated to short is 16 bits.
                      default value for short is zero -'0
                      Range -32768 to -32767
        
        long          A 64-bit (8-byte) integer value
        
        float         A 32-bit (4-byte) floating-point value
                      declaration - float a = 2.45f;
        
        double        A 64-bit (8-byte) floating-point value
        
        char          Memory size allocated to char is 16 bits.
                      default value for char is blank space ('\u0000').
                      declaration - char b ='z';
        
        boolean       A true or false value
                      Default value for boolean is 'false'.
                      declaration - boolean a =true;

Default values for these data types :

    public class Datatype_Default_Value {
    
          static boolean bool;
          static byte by;
          static char ch;
          static double d;
          static float f;
          static int i;
          static long l;
          static short sh;
          static String str;
    
          public static void main(String[] args) {
          
            System.out.println("bool = " + bool);
            System.out.println("by = " + by);
            System.out.println("ch = " + ch);
            System.out.println("d = " + d);
            System.out.println("f = " + f);
            System.out.println("i = " + i);
            System.out.println("l = " + l);
            System.out.println("sh = " + sh);
            System.out.println("str = " + str);
            
          }
    }

OUTPUT :

    bool = false
    by = 0
    ch = 
    d = 0.0
    f = 0.0
    i = 0
    l = 0
    sh = 0
    str = null

WRAPPER CLASSES :

With the use of Wrapper class in java we can convert primitive datatypes into object and object into primitive datatypes.
Java is an object-oriented language and take everything as an object. The primitive data types are not objects they do not belong to any class.
Whenever, the data type is required as an object then we will use wrapper classes to convert primitive datatypes into object and object into primitive datatypes.

     public class Wrapper_Classes {
     
        public static void main(String[] argv)  {
            
            Boolean refBoolean = new Boolean(true);
         // return primitive boolean value of Boolean object
            boolean bool = refBoolean.booleanValue();
            
            System.out.println("bool = " + bool);
            
            Byte refByte = new Byte((byte) 123);
         // return primitive byte value of Byte object
            byte b = refByte.byteValue();
            
            System.out.println("b = " + b);
            
            Character refChar = new Character('x');
         // return value of Character object  
            char c = refChar.charValue();
            
            System.out.println("c = " + c);
            
            Short refShort = new Short((short) 123);
         // return primitive sort value of Short object    
            short s = refShort.shortValue();
            
            System.out.println("s = " + s);
            
            Integer refInt = new Integer(123);
         // return primitive int value of Integer object    
            int i = refInt.intValue();
            
            System.out.println("i = " + i);
            
            Long refLong = new Long(123L);
         // return primitive long value of Long object 
            long l = refLong.longValue();
            
            System.out.println("l = " + l);
            
            Float refFloat = new Float(12.3F);
         // return primitive float value of Float object 
            float f = refFloat.floatValue();
            
            System.out.println("f = " + f);
            
            Double refDouble = new Double(12.3D);
         // return primitive double  value of Double object 
            double d = refDouble.doubleValue();
            
            System.out.println("d = " + d);
          }
    }

OUTPUT :

    bool = true
    b = 123
    c = x
    s = 123
    i = 123
    l = 123
    f = 12.3
    d = 12.3

DATATYPE VALUES RANGE :

Showing java primitive datatypes minimum and maximum values.

   
    public class Min_Max_Value_Datatypes {
        
              public static void main(String[] args) {
                  
                System.out.println("Byte.MIN = " + Byte.MIN_VALUE);
                System.out.println("Byte.MAX = " + Byte.MAX_VALUE);
                System.out.println("Short.MIN = " + Short.MIN_VALUE);
                System.out.println("Short.MAX = " + Short.MAX_VALUE);
                System.out.println("Integer.MIN = " + Integer.MIN_VALUE);
                System.out.println("Integer.MAX = " + Integer.MAX_VALUE);
                System.out.println("Long.MIN = " + Long.MIN_VALUE);
                System.out.println("Long.MAX = " + Long.MAX_VALUE);
                System.out.println("Float.MIN = " + Float.MIN_VALUE);
                System.out.println("Float.MAX = " + Float.MAX_VALUE);
                System.out.println("Double.MIN = " + Double.MIN_VALUE);
                System.out.println("Double.MAX = " + Double.MAX_VALUE);
                
              }
            
    } 

OUTPUT :

    Byte.MIN = -128
    Byte.MAX = 127
    Short.MIN = -32768
    Short.MAX = 32767
    Integer.MIN = -2147483648
    Integer.MAX = 2147483647
    Long.MIN = -9223372036854775808
    Long.MAX = 9223372036854775807
    Float.MIN = 1.4E-45
    Float.MAX = 3.4028235E38
    Double.MIN = 4.9E-324
    Double.MAX = 1.7976931348623157E308