Values and Data Types

ASCII Codes

ASCII stands for American Standard Code for Information Interchange. It uses 7 bits code for representing each character. It includes 256 characters but only 128 characters are used while designing and executing a program. ASCII code represents these characters as numbers, with each letter assigned a number from 0 to 127. The ASCII codes of some of the characters used in Java programming are shown below:

Characters	ASCII Codes
Blank space (white space)	32
0 to 9 (Numbers)	48 – 57
A to Z (Capital Alphabets)	65 – 90
a to z (Small Alphabets)	97 – 122

Tokens

Token is defined as each individual item or component of Java program that carries some meaning and takes active part in program execution.

Keywords

Keywords are the reserved words which are preserved by the system and carry special meaning for the system compiler. They have already been defined in the language and we cannot use them as names for variables or identifiers, e.g., class, public, throws, for, sqrt, etc.

Identifiers

Identifiers is a term used for naming a block of statements by which they are identified in a Java program. Identifiers can be a class name, a function name, an object , a variable name or an interface name. Following are some naming rules for identifiers:

1.       Identifier’s name cannot be same with Keywords or Reserved words.
2.       Identifier’s name always starts with alphabets, not with numbers.
3.        No special characters are used within an identifiers name except underscore (_) or dollar ($).
4.       Blank space (white space) is not allowed in between identifiers name.

Literals

The term constants are referred to as literals in Java programs that remain unchanged during entire execution of the program.

The various types of literals used in Java are as follows:

Integer Literals: The whole numbers (positive or negative) are known as integer literals. Decimal point is not allowed in Integer Literals. e.g., 16, 357, 7856, 66845, etc.

Real Literals: Real literals are also called as floating point numbers. They are the fractional numbers. The placement of decimal point may not be same in real numbers. e.g., 3.45, 85.6, 557.65, etc.

Character Literals: A single letter or a digit or any special symbol enclosed within single quotes is known as a character literal. It does not take part in arithmetical calculations. e.g., ‘B’, ‘u’ ‘6’, ‘?’, etc.

String Literals: A group of characters enclosed within double quotes is known as a String literal. e.g., “PROCESS”, “System”, “Salary – 2018”, “4357”, etc.

Boolean Literals: Boolean literals are true and false. A Boolean literal can either be true or false at a time.

Null Literal: Null literal denotes the absence of a value. It is used to initialize an object or array.

e.g., int n = null;

String s = null;

Operators
Operators are the symbols or signs used to specify the operations to be performed in a Java expression or statement.
To know different types of operators and their functions, click here.

Punctuators or Separators
Punctuators or Separators are some punctuation signs or some special characters in Java, which are used to separate the variables or the characters. e.g., comma (,), semicolon (;), dot (.), parenthesis (), brackets {}, etc.

Data Types

Date type basically refers to as the types of data,a memory location can hold. Java supports mainly following two types of data:

1. Primitive Data Type (Built-in)
2. Non-primitive Data Type (User-defined)

Primitive Data Types

Primitive Data Types are the basic or fundamental data types used to declare a variable. There are following 8 primitive data types present in Java:

Types		Size (Bytes)	Default
Integer	byte	1	0
	short	2	0
	int	4	0
	long	8	0
Real	float	4	0.0
	double	8	0.0
Character	char	2	\u0000
Boolean	boolean	1 bit	false

Non-primitive Data Types

A non-primitive data type is one that is derived from primitive data types. We also may say that a number of primitive data types are used together to represent a non-primitive data type. Hence, a non-primitive data type is also called a composite data type.

Type conversion

If various types of data are used in an expression, a question obviously comes to your mind that what type of result it will return after execution. In fact, the system converts the result into a specific data type known as Type Conversion. Basically, the data type conversion take place in two ways as discussed below:

Implicit type conversion

In a mixed mode expression, when the smaller data types are converted into higher data type automatically, then it is known as Implicit type conversion. It is also known as Coercion.

e.g., int a;

long b;

long c = a + b;

Explicit type conversion

In a mixed mode expression, when the smaller data types are need to be converted into smaller data type, which is normally not possible, then we convert them forcefully using type cast operator (). This is known as Explicit type conversion. It is also known as Type casting.

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Hi, Its me Hafeez. A webdesigner, blogspot developer and UI/UX Designer. I am a certified Themeforest top Author and Front-End Developer. I'am business speaker, marketer, Blogger and Javascript Programmer.

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