DATA TYPES

DATA TYPES:-

Every variable has a type, every expression has a type and all types are strictly define more over every assignment should be checked by the compiler by the type compatibility hence java language is considered as strongly typed programming language.

Java is pure object oriented programming or not?  

Java is not considered as pure object oriented programming language because several oops features (like multiple inheritance, operator overloading) are not supported by java moreover we are depending on primitive data types which are non objects. 

Diagram: 

Except Boolean and char all remaining data types are considered as signed data types because we can represent both "+ve" and"-ve" numbers. 

Integral data types :

Byte:

Size: 1byte (8bits)

Maxvalue: +127 

Minvalue: -128 

Range: -128to 127[2⁷ to 2⁷-1]

• The most significant bit acts as sign bit. "0" means "+ve" number and "1" means "–ve" number.  
• "+ve" numbers will be represented directly in the memory whereas "–ve" numbers will be represented in 2's complement form.

Example:

 byte b=10;

 byte b2=130;//C.E:possible loss of precision found : int ,required : byte 

 C.E=COMPILE TIME ERROR.

byte b=10.5;//C.E:possible loss of precision 

byte b=true;//C.E:incompatible types 

byte b="rehan";//C.E:incompatible types 

 found : java.lang.String required : byte

byte data type is best suitable if we are handling data in terms of streams either from the file or from the network.  

Short: 

The most rarely used data type in java is short. 

Size: 2 bytes 

Range: -32768 to 32767(2¹⁵ to 2¹⁵-1)

Example:

short s=130;

short s=32768;//C.E:possible loss of precision

short s=true;//C.E:incompatible types 

Short data type is best suitable for 16 bit processors like 8086 but these processors are completely outdated and hence the corresponding short data type is also out data type.

Int: 

This is most commonly used data type in java. 

Size: 4 bytes

Range:-2147483648 to 2147483647 (-2³¹ to 2³¹-1) 

Example: int i=130;

int i=10.5;//C.E:possible loss of precision 

int i=true;//C.E:incompatible types

long:

Whenever int is not enough to hold big values then we should go for long data type. 

Example: 

To hold the no. Of characters present in a big file int may not enough hence the return type of length() method is long.

long l=f.length();//f is a file

Size: 8 bytes

Range:-2⁶³to 2⁶³-1 

Note: All the above data types (byte, short, int and long) can be used to represent whole numbers. If we want to represent real numbers then we should go for floating point data types.  

Floating Point Data types:

   

boolean data type: 

Size: Not applicable (virtual machine dependent) 

Range: Not applicable but allowed values are true or false.

Which of the following boolean declarations are valid?

Example 1: 

boolean b=true; 

boolean b=True;//C.E:cannot find symbol

boolean b="True";//C.E:incompatible types 

boolean b=0;//C.E:incompatible types

Example 2: 

                   

Char data type:

• In old languages like C & C++ are ASCII code based the no.Of ASCII code characters are < 256 to represent these 256 characters 8 - bits enough hence char size in old languages 1 byte.
•  In java we are allowed to use any worldwide alphabets character and java is Unicode based and no.Of unicode characters are > 256 and <= 65536 to represent all these characters one byte is not enough compulsory we should go for 2 bytes

Size: 2 bytes 

Range: 0 to 65535

Example: 

char ch1=97; 

char ch2=65536;//C.E:possible loss of precision 

Summary of java primitive data type: