Character Class in Java

The Character class in Java, available in the java.lang package is a wrapper class used to represent a single char value as an object. It provides several useful static methods for character manipulation and supports automatic conversion between primitive and object types.

• Wrapper for char: A Character object wraps a single primitive char value and allows it to be used in object-oriented contexts.
• Object creation: Earlier, objects were created using new Character(char), but this constructor is deprecated; use Character.valueOf(char) instead.
• Utility methods: The class provides static methods like isDigit(), isLetter(), toUpperCase(), and toLowerCase() for character operations.
• Autoboxing and unboxing: Java automatically converts between char and Character when required, simplifying code and improving readability.

Syntax

Character.methodName(parameter)

• Parameter: char
• Return type: boolean, char, or int depending on the method

Note: Character class is immutable like String class i.e once it's object is created, it cannot be changed.

Commonly Used Methods in Character Class

1. boolean isLetter(char ch): This method is used to determine whether the specified char value(ch) is a letter or not. The method will return true if it is letter([A-Z],[a-z]), otherwise return false. In place of character, we can also pass ASCII value as an argument as char to int is implicitly typecasted in java.

Syntax: 

boolean isLetter(char ch)

• Parameters: ch - a primitive character
• Return Type: It returns true if ch is an alphabet, otherwise, return false

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.isLetter('A'));
        System.out.println(Character.isLetter('0'));
    }
}

true
false

2. boolean isDigit(char ch): This method is used to determine whether the specified char value(ch) is a digit or not. Here also we can pass ASCII value as an argument. 

Syntax: 

boolean isDigit(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns true if ch is a digit, otherwise, return false

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.isDigit('A'));
        System.out.println(Character.isDigit('0'));
    }
}

false
true

3. boolean isWhitespace(char ch): It determines whether the specified char value(ch) is white space. Whitespace includes space, tab, or newline. 

Syntax: 

boolean isWhitespace(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns true if ch is whitespace, otherwise, returns false.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.isWhitespace('A'));
        System.out.println(Character.isWhitespace(' '));
        System.out.println(Character.isWhitespace('\n'));
        System.out.println(Character.isWhitespace('\t'));
        System.out.println(Character.isWhitespace(9));
        System.out.println(Character.isWhitespace('9'));
    }
}

false
true
true
true
true
false

4. boolean isUpperCase(char ch): It determines whether the specified char value(ch) is uppercase or not. 

Syntax: 

boolean isUpperCase(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns true if ch is upper case, otherwise, returns false.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.isUpperCase('A'));
        System.out.println(Character.isUpperCase('a'));
        System.out.println(Character.isUpperCase(65));
    }
}

true
false
true

5. boolean isLowerCase(char ch): It determines whether the specified char value(ch) is lowercase or not. 

Syntax: 

boolean isLowerCase(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns true if ch is lower case, otherwise, returns false.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.isLowerCase('A'));
        System.out.println(Character.isLowerCase('a'));
        System.out.println(Character.isLowerCase(97));
    }
}

false
true
true

6. char toUpperCase(char ch): It returns the uppercase of the specified char value(ch). If an ASCII value is passed, then the ASCII value of its uppercase will be returned. 

Syntax: 

char toUpperCase(char ch)

• Parameters: ch - a primitive character
• Return Type: It returns the uppercase form of the specified char value.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.toUpperCase('a'));
        System.out.println(Character.toUpperCase(97));
        System.out.println(Character.toUpperCase(48));
    }
}

A
65
48

7. char toLowerCase(char ch): It returns the lowercase of the specified char value(ch). 

Syntax: 

char toLowerCase(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns the lowercase form of the specified char value.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.toLowerCase('A'));
        System.out.println(Character.toLowerCase(65));
        System.out.println(Character.toLowerCase(48));
    }
}

a
97
48

8. toString(char ch): It returns a String class object representing the specified character value(ch) i.e a one-character string. Here we cannot pass ASCII value. 

Syntax: 

String toString(char ch)

• Parameter: ch - a primitive character
• Return Type: It returns a String object.

public class Test {
    public static void main(String[] args) {
        System.out.println(Character.toString('x'));
        System.out.println(Character.toString('Y'));
    }
}

x
Y

Methods of Character Class in Java