In Java Programming, Literals (often referred to as constants) are data items that are fixed data values. Java allows several kinds of literals:

A real literal in fraction form consist of signed or unsigned digits including a decimal point between digits. The rule for writing a real constant in fraction from is given below:

Invalid real constants contains 7, (7.), +17/2, 250.26.2, (17,250.262)

A real literals in exponent form consists of two parts: mantissa and exponent. For instance 5.8 can be written as 0.58 X 10 = o.58E01 where mantissa part is 0.58 (the part appearing before E) and exponent part is 1(the part appearing after E). E01 represent 10 1 . The rule for writing a real literal in exponent from is given below:

Invalid real literals in exponent from:

(i) 172.E5 (at least a digit must follow the decimal point)

(ii) 1.7E (no digit specified for exponent)

(iii) 0.17E2.3 (exponent cannot have fraction part)

(iv) 17,225E02 (no comma allowed)

(v) .25E-7 (no preceding digits before decimal point)

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- Integer-literal
- Floating-literals
- Boolean-literals
- Character-literals
- Strings-literal
- Null literals

#### Integer Literals

Integer literals are whole numbers without any fractional part. The method of writing integer constants has been specified in the following rule.An integer constant must have at least one more digit and must not contain any decimal point. It may contain either + or – sing. A number with no sing is assumed to be positive. Commas cannot appear in an integer constant.Java allows three types of integer literals:

- An integer literal consisting of a sequence of digit is taken to be decimal integer constant unless it begins with 0(digit zero). For instance, 1234, 41, +97,-17 are decimal integer literals.
- A sequence of digit starting with 0(digit zero) is taken to be an octal integer. For instance decimal integer 8 will be written as 010 as octal integer (810 =108) and decimal integer 12 will be written as 014 as octal integer (1210 = 1410). But make sure that when an integer begins with 0, it must not contain 8 and 9 as these are invalid octal digits.
- A sequence of digit preceded by 0x or OX is taken to be a hexadecimal integer. For instance decimal 12 will be written as 0XC as hexadecimal integer. But with Hexadecimal constants only 0-9 and A-F can be used. All other letters are illegal.

#### Floating Literals

Floating literals are also called real literals. Real literals are numbers having fractional parts. These may be written in one of the two forms called fractional form or the exponent form.A real literal in fraction form consist of signed or unsigned digits including a decimal point between digits. The rule for writing a real constant in fraction from is given below:

A real literal in fraction form must have at least one digit before a decimal point and at last one digit after decimal point. It may also have either + or – sign preceding it. A real literal with no sign is assumed to be positive.Valid real literals in fraction form contains 2.0, 17.5, -13.0, -0.00625

Invalid real constants contains 7, (7.), +17/2, 250.26.2, (17,250.262)

A real literals in exponent form consists of two parts: mantissa and exponent. For instance 5.8 can be written as 0.58 X 10 = o.58E01 where mantissa part is 0.58 (the part appearing before E) and exponent part is 1(the part appearing after E). E01 represent 10 1 . The rule for writing a real literal in exponent from is given below:

A real literal in exponent from has two parts: a mantissa and an exponent. The mantissa must be either must be an integer or a proper real literal. The mantissa is followed by a letter E or e and the exponent. The exponent must be an integer.Valid real literals in exponent form: 152E05, 1.52E07, 0,152E08, 152.0E08, 152E+8, 1520E04

Invalid real literals in exponent from:

(i) 172.E5 (at least a digit must follow the decimal point)

(ii) 1.7E (no digit specified for exponent)

(iii) 0.17E2.3 (exponent cannot have fraction part)

(iv) 17,225E02 (no comma allowed)

(v) .25E-7 (no preceding digits before decimal point)

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