Data Types in Java

Primitive Data types:

In Java there are eight (8) primitive data types. For all those primitive data types wrapper classes also available.

If you define the primitive data types as global variables they hold some default values which are given below.

/* Primitive data types and their default values*/
static byte by; //0
static char c; // space
static short sh; //0
static int i; //0
static long l; //0
static float f; //0.0
static double d; //0.0
static boolean b; //false

Note: If you define the primitive data types as local variables they hold nothing and you must initialize them.

Wrapper Classes (Non Primitive Data types):

If you define the wrapper class data types as global variables then they hold some default values which is null

 /* Wrapper Class data types */
static Byte by1; //null
static Character c1; //null
static Short sh1; //null
static Integer i1; //null
static Long l1; //null
static Float f1; //null
static Double d1; //null
static Boolean b1; //null

static BigDecimal bd; //null
static String s; //null

Note: If you define these wrapper class data types as local variables they hold nothing and you must initialize them.  There are few more wrapper classes like Array, List etc.