By literal we mean any number, text, or other information that represents a value. This means what you type is what you get. We will use literals in addition to variables in Java statement. While writing a source code as a character sequence, we can specify any value as a literal such as an integer. This character sequence will specify the syntax based on the value's type. This will give a literal as a result. For instance
int month = 10;
In the above statement the literal is an integer value i.e 10. The literal is 10 because it directly represents the integer value.
In Java programming language there are some special type of literals that represent numbers, characters, strings and boolean values. Lets have a closer look on each of the following.
Number literals is a sequence of digits and a suffix as L. To represent the type as long integer we use L as a suffix. We can specify the integers either in decimal, hexadecimal or octal format. To indicate a decimal format put the left most digit as nonzero. Similarly put the characters as ox to the left of at least one hexadecimal digit to indicate hexadecimal format. Also we can indicate the octal format by a zero digit followed by the digits 0 to 7. Lets tweak the table below.
|659L||Decimal integer literal of type long integer|
|0x4a||Hexadecimal integer literal of type integer|
|057L||Octal integer literal of type long integer|
We can specify a character literal as a single printable character in a pair of single quote characters such as 'a', '#', and '3'. You must be knowing about the ASCII character set. The ASCII character set includes 128 characters including letters, numerals, punctuations etc. There are few character literals which are not readily printable through a keyboard. The table below shows the codes that can represent these special characters. The letter d such as in the octal, hex etc represents a number.
|\'||Single quotation mark|
|\"||Double quotation mark|
It is very interesting to know that if we want to specify a single quote, a backslash, or a nonprintable character
as a character literal use an escape sequence. An escape sequence uses a
special syntax to represents a character. The syntax begins with a single backslash character.
Lets see the table below in which the character literals use Unicode escape sequence to represent printable and nonprintable characters both.
|'u0041'||Capital letter A|
|'\u0022'||Double quote "|
The values true and false are also treated as literals in Java programming. When we assign a value to a boolean variable, we can only use these two values. Unlike C, we can't presume that the value of 1 is equivalent to true and 0 is equivalent to false in Java. We have to use the values true and false to represent a Boolean value. Like
boolean chosen = true;
Remember that the literal true is not represented by the quotation marks around it. The Java compiler will take it as a string of characters, if its in quotation marks.
Floating-point numbers are like real numbers in mathematics, for example, 4.13179, -0.000001. Java has two kinds of floating-point numbers: float and double. The default type when you write a floating-point literal is double.
|in decimal digits|
+/- 3.4 * 1038
+/- 1.8 * 10308
A floating-point literal can be denoted as a
decimal point, a fraction part, an exponent (represented by E or e) and as an
integer. We also add a suffix to the floating point literal as D, d, F or
f. The type of a floating-point literal defaults to double-precision floating-point.
The following floating-point literals represent double-precision floating-point and floating-point values.
|6.5E+32 (or 6.5E32)||Double-precision floating-point literal|
|7D||Double-precision floating-point literal|
The string of characters is represented as String literals in Java. In Java a string is not a basic data type, rather it is an object. These strings are not stored in arrays as in C language. There are few methods provided in Java to combine strings, modify strings and to know whether to strings have the same value.
We represent string literals as
String myString = "How are you?";
The above example shows how to represent a string. It consists of a series of characters inside double quotation marks.
Lets see some more examples of string literals:
"" // the empty string
"\"" // a string containing "
"This is a string" // a string containing 16 characters
"This is a " + // actually a string-valued constant expression,
"two-line string" // formed from two string literals
Strings can include the character escape codes as well,
as shown here:
String example = "Your Name, \"Sumit\"";
The final literal that we can use in Java programming is a Null literal. We specify the Null literal in the source code as 'null'. To reduce the number of references to an object, use null literal. The type of the null literal is always null. We typically assign null literals to object reference variables. For instance
s = null;
An this example an object is referenced by s. We reduce the number of references to an object by assigning null to s. Now, as in this example the object is no longer referenced so it will be available for the garbage collection i.e. the compiler will destroy it and the free memory will be allocated to the other object. Well, we will later learn about garbage collection.