Character Class in Java

Java provides a wrapper class Character in java.lang package. An object of type Character contains a single field, whose type is char. The Character class offers a number of useful class (i.e., static) methods for manipulating characters. You can create a Character object with the Character constructor.

Creating a Character object: 

Character ch = new Character('a');

The above statement creates a Character object which contains 'a' of type char. There is only one constructor in the Character class that expects an argument of char data type.

If we pass a primitive char into a method that expects an object, the compiler automatically converts the char to a Character class object. This feature is called Autoboxing and Unboxing.

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

Methods in Character Class  

The methods of Character class are as follows:

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

Returns: It returns true if ch is an alphabet, otherwise, return false

Example:

// Java program to demonstrate isLetter() method

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)

Parameters: 

• ch - a primitive character

Returns: It returns true if ch is a digit, otherwise, return false

Example:

// Java program to demonstrate isDigit() method

public class Test {
    public static void main(String[] args)
    {
        // print false as A is character
        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)

Parameters: 

• ch - a primitive character

Returns: It returns true if ch is whitespace, otherwise, returns false.

Example:

// Java program to demonstrate isWhitespace() method

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'));

        // ASCII value of tab
        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)

Parameters: 

• ch - a primitive character

Returns: It returns true if ch is upper case, otherwise, returns false.

Example:

// Java program to demonstrate isUpperCase() method

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)

Parameters: 

• ch - a primitive character

Returns: It returns true if ch is lower case, otherwise, returns false.

Example:

// Java program to demonstrate isLowerCase() method

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

Returns: It returns the uppercase form of the specified char value.

Example:

// Java program to demonstrate toUpperCase() method

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)

Parameters: 

• ch - a primitive character

Returns: It returns the lowercase form of the specified char value.

Example:

// Java program to demonstrate toLowerCase() method

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)

Parameters: 

• ch - a primitive character

Returns: It returns a String object.

Example:

// Java program to demonstrate toString() method

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

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

She said "Hello!" to me.

you would write

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