Java Primitive and Non Primitive Data Types

Primitive Data Type

Primitive means “very basic”. It is simple and normal types. Value of primitive is stored in memory location or memory location is given to variable.

For example if you want to store 50 in memory location:


int value = 50;

int value = 50;

Primitive data types are further divided into Numeric and Non numeric data types. Under Numeric data types. Int and float. Under non Numeric data types Char and Boolean.

Type	Contains	Default	Size	Range
boolean	true or false	false	1 bit	NA
char	Unicode character	\u0000	16 bits	\u0000 to \uFFFF
byte	Signed Integer	0	8 bits	-128 to 127
short	Signed Integer	0	16 bits	-32768 to 32767
int	Signed Integer	0	32 bits	-2147483648 to 2147483647
long	Signed Integer	0	64 bits	-9223372036854775808 to 9223372036854775807
float	IEEE 754 Floating Point	0.0	32 bits	approximately ±3.40282347E+38F (6-7 significant decimal digits) Java implements IEEE 754 standard
double	IEEE 754 Floating Point	0.0	64 bits	approximately ±1.79769313486231570E+308 (15 significant decimal digits)

Non Primitive Data Type

It is useful when using them as generic types(including Collection classes, such as lists and maps) or when you want to transform them to other type without implicit casting (for example Integer class has methods doubleValue() or byteValue().

Non Primitive data types are also known as Reference which is created by the user itself.

Java

Integer value = new Integer(50);

0
1
2

Integer value = new Integer(50);

Conclusion

In Item 5, of Effective Java, Joshua Bloch says Prefer primitives to boxed primitives, and watch out for unintentional autoboxing.


public static void main(String[] args) {
		Long sum = 0L;
		for (long i = 0; i < Integer.MAX_VALUE; i++) {
			sum += i;
		}
		System.out.println(sum);
	}

public static void main(String[] args) {

Long sum = 0L;

for (long i = 0; i < Integer.MAX_VALUE; i++) {

sum += i;

}

System.out.println(sum);

}

This program gets the right answer, but it is much slower than it should be, due to a one-character typographical error. The variable sum is declared as a Long instead of a long, which means that the program constructs about 2^31 unnecessary Long instances (roughly one for each time the long i is added to the Long sum). Changing the declaration of sum from Long to long reduces the run time from 43 seconds to 6.8 seconds on my machine.

The fact is it is slower to use the Object wrappers for primitives than just using the primitives. You’re adding the cost of object instantiation, method calls, etc. to things that you use all over the place. You use the wrappers when you need to add things to collections.