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Data Types in Java

Information that program receives or processed outputs are stored in memory location with some pointer or name to access it, known as Variable. value of variable is prone to change any number of times in lifetime of program.

Information can be sequence of character(Strings), numbers, or true or false boolean values.

In Java, when you declare a variable you need to declare the type of data or information that it will hold, so Java compiler can understand the what type of information will store in declared variables pointing memory location an in turn JVM allocates that much size of memory,  as every data type has its own limitation or you can say size of data that it can hold.

We will see soon below what different types of data types that Java support and their data size limitations.

In Java there are two data types available:
  1. Primitive data type
  2. Reference data type.

Primitive Data Type:

In Java there are eight primitive data types available to serve different types of data natively. primitive data types also called native data types and are reserved as keywords in Java language.primitive data type store only primitive values, you might seen same data types in other languages like C/C++ or python etc.

Boolean Data Type:

  • boolean:

    • 1 bit information
    • Default value : false
    • Typically boolean data types use to represent flags in programs, mostly use in if...else if...else construct
    • e.g. boolean isDoorOpen = true;

Character Data Type:

  • char:

    • Java uses Unicode system than ASCII for char data type
    • Size of char is 16 bit (2 byte) unicode character.
    • Default value : '\u0000'
    •  \u0000 is lowest range of character in Unicode character system
    • Enclose char with single quote
    • e.g. char a = 'a' ; char A = 'A'; 

Number Data Type(Non floating point):

  • byte:

    • 8 bit (1 byte) signed twos complement number
    • Default value :  0
    • Minimum value : -128 (-2^8-1)
    • Maximum value : 127(2^8-2)
    • byte data type is smallest data type available in Java, use it wherever only when you feel confident that the data will be in range of -128 to 127, using larger data type to store small data is mere just waste of memory.
    • if you try to store number larger than max limit then overflow effect will happen, soon we will see with example how overflow effect happens.
    • e.g. byte numberOfTyres = 4 , e = -27;

  • short:

    • 16 bit (2 byte) signed twos complement number
    • Default value : 0
    • Minimum value : -32,768 (-2^16-1)
    • Maximum value : 32, 767(2^16-2)
    • if you try to store number larger than max limit then overflow effect will happen, soon we will see with example how overflow effect happens.
    • e.g. short sum = 21000;

  • int:

    • 32 bit(4 byte) signed twos complement number
    • Default value : 0
    • Minimum value : -2,147,483,648 (-2^32-1)
    • Maximum value : -2,147,483,647 (-2^32-2)
    • if you try to store number larger than max limit then overflow effect will happen, soon we will see with example how overflow effect happens.
    •  e.g. int numberOfNodes = 3700000;

  • long:

    • 64 bit(8 byte) signed twos complement number
    • Default value : 0L or 0l
    • L or l represent long against number.
    • Minimum value : -9,223,372,036,854,775,808 (-2^64-1)
    • Maximum value : -9,223,372,036,854,775,808 (-2^64-2)
    • be careful when using long data as its largest data type available in Java, double in size than int. use it when needed
    • e.g long  dailyVisitors = 33444343234444L;

Number Data Type(floating point):

  • float:

    • 32 bit(4 byte) single precision IEEE-754 floating point number
    • Default value : 0.0f
    • f or F represent float against number
    • e.g. float s = 33.44f, d = 3.14F

  • double:

    • 64 bit(8 byte) single precision IEEE-754 floating point number
    • Default value : 0.0d
    • d or D represent double against number
    • e.g double d = 13.45d, e = 44.12D
Overflow effect:
Output:
So far, we have seen about primitive data type, i will continue for Reference data type in more details in next post. 
Thanks for reading post!



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