Escape special characters in java

Java Special Characters

Because strings must be written within quotes, Java will misunderstand this string, and generate an error:

String txt = "We are the so-called "Vikings" from the north."; 

The solution to avoid this problem, is to use the backslash escape character.

The backslash ( \ ) escape character turns special characters into string characters:

The sequence \» inserts a double quote in a string:

Example

String txt = "We are the so-called \"Vikings\" from the north."; 

The sequence \’ inserts a single quote in a string:

Example

The sequence \\ inserts a single backslash in a string:

Example

String txt = "The character \\ is called backslash."; 

Other common escape sequences that are valid in Java are:

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Characters

Most of the time, if you are using a single character value, you will use the primitive char type. For example:

char ch = 'a'; // Unicode for uppercase Greek omega character char uniChar = '\u03A9'; // an array of chars char[] charArray = < 'a', 'b', 'c', 'd', 'e' >;

There are times, however, when you need to use a char as an object—for example, as a method argument where an object is expected. The Java programming language provides a wrapper class that «wraps» the char in a Character object for this purpose. An object of type Character contains a single field, whose type is char . This Character class also offers a number of useful class (that is, static) methods for manipulating characters.

You can create a Character object with the Character constructor:

Character ch = new Character('a');

The Java compiler will also create a Character object for you under some circumstances. For example, if you pass a primitive char into a method that expects an object, the compiler automatically converts the char to a Character for you. This feature is called autoboxing—or unboxing, if the conversion goes the other way. For more information on autoboxing and unboxing, see Autoboxing and Unboxing.

Note: The Character class is immutable, so that once it is created, a Character object cannot be changed.

The following table lists some of the most useful methods in the Character class, but is not exhaustive. For a complete listing of all methods in this class (there are more than 50), refer to the java.lang.Character API specification.

Escape Sequences

A character preceded by a backslash (\) is an escape sequence and has special meaning to the compiler. The following table shows the Java escape sequences:

When an escape sequence is encountered in a print statement, the compiler interprets it accordingly. For example, if you want to put quotes within quotes you must use the escape sequence, \», on the interior quotes. To print the sentence

System.out.println("She said \"Hello!\" to me.");

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Working with Strings and Special Characters in Java

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Whether you create a String using the constructor or as a string literal, the most important thing to remember is that the entire sequence must be enclosed in quotation marks. This can pose a problem if the string itself must contain quotation marks. That is where character escaping comes in. Besides quotation marks, you can insert several special characters into a string in the same way. We will be looking at character escaping, escape characters, and special characters in this Java programming tutorial.

Character Escaping in Java

In Java, as in many other programming languages, character escaping is accomplished using the “backslash” (\) symbol. In Java, a backslash, combined with a character to be “escaped”, is called a control sequence. For example, \” is a control sequence for displaying quotation marks in a String. The control sequence tells the compiler that the quotation mark should be included as part of the String. Here is some example code that prints my favorite movie to the screen showing how to use escape characters in Java:

public class DoubleQuotesExample < public static void main(String[] args) < String myFavoriteMovie = "My favorite movie is \"Raiders of the Lost Ark\"."; System.out.println(myFavoriteMovie); // Outputs My favorite movie is "Raiders of the Lost Ark". > >

Special Characters in Java

Some characters, like the quotation mark, are part of the Java language; others, like the new line character, are simply a regular letter – the letter n in this case. However, when combined with the backslash symbol, these special characters tell the compiler to treat them differently than it usually would. When the compiler encounters \n in the text, it understands that this is not just a symbol and a letter to display in the console, but rather, a special command to start a new line – equivalent to pressing Enter. For example, this example Java code shows how to use the newline special character \n to to display the lyrics of a song:

public class NewLineExample < public static void main(String[] args) < String lyric I:\My Documents\quarterly reports\Q1.rpt";

Since the compiler does not recognize \ as anything other than a control sequence, it expects the backslash to be followed by a special character to be interpreted in a certain way. However, in this case, \ is followed by ordinary letters. The solution? Exactly the same as before: we just escape the \ character!

public class BackslashExample < public static void main(String[] args) < String reportPath = "I:\\My Documents\\quarterly reports\\Q1.rpt"; System.out.println(reportPath); // Outputs I:\My Documents\quarterly reports\Q1.rpt > >

Here is the full list of special characters in Java:

The code example below shows how to use several of these special characters in Java:

public class SpecialCharactersExample < public static void main(String[] args) < String strWithTabs = "Header1\tHeader2\tHeader3"; System.out.println(strWithTabs); // Outputs Header1 Header2 Header3 String strWithNewLines = "As I walk,\nmy life drifts\nbefore me"; System.out.println(strWithNewLines); /* Outputs: As I walk, my life drifts before me */ String strWithBackslash = "And\\Or"; System.out.println(strWithBackslash); // Outputs And\Or String strWithCarriageReturn = "Carriage\rReturn"; System.out.println(strWithCarriageReturn); /* Outputs: Carriage Return */ String strWithSingleQuote = "Other people\'s money"; System.out.println(strWithSingleQuote); // Outputs Other people's money String strWithDoubleQuotes = "Dwayne \"The Rock\" Johnson"; System.out.println(strWithDoubleQuotes); // Outputs Dwayne "The Rock" Johnson > >

Escaping Unicode Characters in Java

Unicode is a standard character encoding that includes the symbols of practically every written language in the world. All Unicode character codes have the form “u+ “. For example, the copyright symbol (©) is represented by u00A9. To include this character in a Java String, you need to escape it, as seen in the following code example:

public class CopyrightExample < public static void main(String[] args) < System.out.println("\"Star Wars\", \u00A9 1977 All Rights Reserved"); // Outputs "Star Wars", © 1977 All Rights Reserved >>

public class UnicodeCharactersExample < public static void main(String[] args) < char forwardSlash = '\u002F'; System.out.println(forwardSlash); // Outputs / char questionMark = '\u003F'; System.out.println(questionMark); // Outputs ? char number1 = '\u0031'; System.out.println(number1); // Outputs 1 char tilde = '\u007E'; System.out.println(tilde); // Outputs ~ char dollarSign = '\u0024'; System.out.println(dollarSign); // Outputs $ char lowercaseA = '\u0061'; System.out.println(lowercaseA); // Outputs a char uppercaseA = '\u0041'; System.out.println(uppercaseA); // Outputs A char japaneseYen = '\u00a5'; System.out.println(japaneseYen); // Outputs ¥ char romanAeWithAcuteAccent = '\u01FC'; System.out.println(romanAeWithAcuteAccent); // Outputs Ǽ char greekCapitalAlpha = '\u0391'; System.out.println(greekCapitalAlpha); // Outputs Α char greekCapitalOmega = '\u03A9'; System.out.println(greekCapitalOmega); // Outputs Ω > >