CONSTANTS, VARIABLES AND DATA TYPES

Introduction

• A programming language is designed to process certain kind of data consisting of numbers, characters and string and to provide useful output called information

• The task of processing data is accomplished by executing a sequence of instruction known as program.

• The instructions are formed using certain symbols and words according to some rigid rules known as syntax rule or grammar.

• Like any other language java also have its own vocabulary and grammar. Know we will discuss concepts of constants and variable and their data type.

Constants

Integer constantAn integer constant refers to a sequence of digits.

There are three types of integers, namely, decimal integer, octal integer and hexadecimal integer

• Decimal integer: - consist of a set of digit through 0 to 9, which may be proceeded by optional sign minus e.g. 7897,-64864, and 0 etc.

• Octal integer: - consist of a set of digit through 0 to 7, with preceding 0. For example: - 037, 0 0465, etc.

• Hexadecimal integer: - consist of a set of digit through 0 to 9 and A through F or a through f, with preceding 0x or 0X. For example: - 0x37, 0x, 0X465AF, 0xfcb23, etc.

Real ConstantsThe quantities which are represented by numbers containing fraction parts are known as Real or Floating point constant. For example 0.0086, -0.75 etc

• A real number can also be represented in scientific notation like 2.15e2 here e2 means 102.

• The general syntax is

Mantissa e exponent

Character Constants

A single character constant contains a single character enclosed with in a pair of single quote mark. Example: -

‘a’,’A’,’12’

String constant

A string constant is a sequence of character enclosed between double quote. Example:

“hello”, ”java”

Backslash character constant

Java Also Supports Backslash Constants those are used in output methods For Example \n is used for new line

Character. These are also called as escape Sequence or backslash character Constants.

Backslash Code Description

\t tab character

\n new line or line feed character

\r carriage-return character

\f form-feed character

\a alert or bell character

\e escape character

\cx control character corresponding to x

\\ backslash character

\0n character with octal value

\0nn character with octal value

\0mnn character with octal value

\xhh character with hexadecimal value

\uhhhh character with hexadecimal value

Data Types

INTEGER TYPES• An integer is a whole number — that is, a

number with no fractional or decimal portion. Java has four integer types, which you can use to store numbers of varying sizes.

Type Number of

Bytes

Range of Values

byte 1 –128 to +127

short 2 –32,768 to +32,767

int 4 –2 billion to +2 billion

long 8 -9,223,372,036,854,775,808

to 9,223,372,036,854,775,807

Floating point types• Floating-point numbers are numbers that have

fractional parts (usually expressed with a decimal point). You use a floating-point type in Java programs whenever you need a number with a decimal, such as 19.95 or 3.1415.

• Java has two primitive types for floating-point numbers:

• float: Uses 4 bytes• double: Uses 8 bytes

• In almost all cases, you should use the double type whenever you need numbers with fractional values.

Character type

• char data type is a single 16-bit Unicode character.

• Minimum value is '\u0000' (or 0).

• Maximum value is '\uffff' (or 65,535 inclusive).

• Char data type is used to store any character.

• Example . char letterA ='A'

Boolean Type

• Boolean data type represents one bit of information.

• There are only two possible values: true and false.

• This data type is used for simple flags that track true/false conditions.

• Default value is false.

Example : boolean one = true