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Character Class in Java

Introduction​

Java provides a wrapper class Character in the java.lang package. An object of type Character contains a single field whose type is char. The Character class offers various useful static methods for manipulating characters.

Creating a Character Object​

Character ch = new Character('a');

This creates a Character object containing 'a'. The class is immutable like String.

Autoboxing & Unboxing​

If we pass a primitive char into a method expecting an object, Java automatically converts it to a Character object. This feature is called Autoboxing. The reverse process is called Unboxing.

Methods in Character Class​

1. isLetter(char ch)​

Checks if the given character is a letter.

System.out.println(Character.isLetter('A')); // true
System.out.println(Character.isLetter('0')); // false

2. isDigit(char ch)​

Checks if the given character is a digit.

System.out.println(Character.isDigit('A')); // false
System.out.println(Character.isDigit('9')); // true

3. isWhitespace(char ch)​

Checks if the given character is a whitespace.

System.out.println(Character.isWhitespace(' ')); // true
System.out.println(Character.isWhitespace('\t')); // true
System.out.println(Character.isWhitespace('A')); // false

4. isUpperCase(char ch)​

Checks if the given character is an uppercase letter.

System.out.println(Character.isUpperCase('A')); // true
System.out.println(Character.isUpperCase('a')); // false

5. isLowerCase(char ch)​

Checks if the given character is a lowercase letter.

System.out.println(Character.isLowerCase('a')); // true
System.out.println(Character.isLowerCase('A')); // false

6. toUpperCase(char ch)​

Converts the given character to uppercase.

System.out.println(Character.toUpperCase('a')); // A

7. toLowerCase(char ch)​

Converts the given character to lowercase.

System.out.println(Character.toLowerCase('A')); // a

8. toString(char ch)​

Converts the given character to a String.

System.out.println(Character.toString('x')); // "x"

9. isLetterOrDigit(char ch)​

Checks if the character is a letter or digit.

System.out.println(Character.isLetterOrDigit('A')); // true
System.out.println(Character.isLetterOrDigit('1')); // true
System.out.println(Character.isLetterOrDigit('@')); // false

10. isJavaIdentifierStart(char ch)​

Checks if the character is a valid start for a Java identifier.

System.out.println(Character.isJavaIdentifierStart('A')); // true
System.out.println(Character.isJavaIdentifierStart('1')); // false

11. isJavaIdentifierPart(char ch)​

Checks if the character is valid within a Java identifier (not the first character).

System.out.println(Character.isJavaIdentifierPart('A')); // true
System.out.println(Character.isJavaIdentifierPart('1')); // true
System.out.println(Character.isJavaIdentifierPart('@')); // false

12. isDefined(char ch)​

Checks if the character is a defined Unicode character.

System.out.println(Character.isDefined('A')); // true
System.out.println(Character.isDefined('\uFFFF')); // false

13. getType(char ch)​

Returns the general category of the character as defined by Unicode.

System.out.println(Character.getType('A')); // 1 (UPPERCASE_LETTER)

14. getNumericValue(char ch)​

Returns the numeric value of a character (e.g., digit characters).

System.out.println(Character.getNumericValue('5')); // 5
System.out.println(Character.getNumericValue('A')); // 10

15. reverseBytes(char ch)​

Reverses the bytes of a character.

System.out.println(Character.reverseBytes('A'));

Escape Sequences​

Escape sequences in Java use a backslash (\).

Escape SequenceDescription
\tInserts a tab
\bInserts a backspace
\nInserts a newline
\rInserts a carriage return
\fInserts a form feed
\'Inserts a single quote
\"Inserts a double quote
\\Inserts a backslash

Example:​

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

Output:

She said "Hello!" to me.

This document provides an overview of the Character class and its key methods with examples.