String Literals and Escape Sequences in Java
In Java, strings are sequences of characters enclosed within double quotes ("). While printing simple strings is straightforward, representing double quotes within a string requires special handling. This tutorial explains how to print strings containing double quotes, and introduces the concept of escape sequences in Java string literals.
Understanding String Literals
A string literal is a sequence of characters enclosed in double quotes. For example:
String message = "Hello, world!";
System.out.println(message); // Output: Hello, world!
However, what if you want to include a double quote character inside the string itself? Directly including it won’t work as intended. Java interprets the closing double quote as the end of the string literal.
Using Escape Sequences
To represent special characters like double quotes within a string, Java uses escape sequences. An escape sequence begins with a backslash (\) followed by a character that represents the special character you want to include.
To include a double quote within a string, you use the escape sequence \".
Here’s how to print the string "Hello":
System.out.println("\"Hello\""); // Output: "Hello"
The backslash \ tells the Java compiler to treat the following double quote as a literal character to be included in the string, rather than the end of the string.
Other Useful Escape Sequences
Besides double quotes, several other characters require escaping:
- Newline:
\n– Moves the cursor to the beginning of the next line. - Tab:
\t– Inserts a horizontal tab. - Backslash:
\\– Represents a literal backslash character. - Single Quote:
\'– Represents a single quote character. - Carriage Return:
\r– Moves the cursor to the beginning of the current line.
Example with Multiple Escape Sequences:
System.out.println("This is a line with a tab\t and a newline\n");
System.out.println("Here's a backslash: \\");
System.out.println("And a single quote: \'");
Unicode Escape Sequences
Java also allows you to represent Unicode characters using escape sequences of the form \uXXXX, where XXXX is a hexadecimal representation of the Unicode code point. For example, to represent a double quote using a Unicode escape sequence, you’d use \u0022.
System.out.print('\u0022' + "Hello" + '\u0022'); // Output: "Hello"
Unicode escape sequences are useful for including characters that are difficult or impossible to represent directly in your source code. They can be used anywhere a character literal is allowed.
Character Literals
You can also use character literals to construct strings containing quotes. A character literal is a single character enclosed in single quotes ( ' ).
char quote = '"';
System.out.println(quote + "Hello" + quote); //Output: "Hello"