char

About

• Definition: char is a Java primitive data type used to store single 16-bit Unicode characters.

• Size: Occupies 2 bytes (16 bits) of memory.

  • This is because Java uses the UTF-16 encoding to support a wide range of Unicode characters.

• Value Range: char can represent any unsigned value between 0 and 65535 ('\u0000' to '\uffff').

• Default Value: The default value for char is '\u0000' (null character).

• Wrapper Class: The wrapper class for char is Character, located in java.lang.

Characteristics

1. Single Character Representation:

   • Can represent any character, including alphabets, digits, symbols, or special Unicode characters.

   • E.g., 'A', '1', '#', '\n'.

2. Integral Type (Unsigned): Internally treated as an unsigned integer and can participate in arithmetic operations.

3. Immutable: Once assigned, the value of a char cannot be altered unless explicitly reassigned.

4. Unicode Compatibility:

   • Fully supports 16-bit Unicode for global character representation.

   • Allows the use of escape sequences like '\uXXXX' to define characters.

5. Integral Representation: Each char is a numeric value. For example:

   char c = 'A'; // 65 in ASCII
   char d = (char) (c + 1); // 'B'

6. Control Characters: Special characters like '\n' (newline), '\t' (tab), and '\r' (carriage return).

7. Memory Usage: Fixed at 2 bytes because it uses UTF-16 encoding.

8. Char Arrays: Arrays of char are commonly used for string manipulation.

Operations with char

Operation	Example	Description
Arithmetic Operations	'A' + 1	Results in 'B' (Numeric addition).
Comparison Operations	'A' > 'a'	Compares the Unicode values of characters.
Type Casting to Int	(int) 'A'	Converts char to its Unicode integer value.
Escape Sequences	'\n', '\t', '\u0041'	Represents special or Unicode characters.

Conversion Methods

Conversion	Method	Example
char to String	Character.toString(c) or String.valueOf(c)	String.valueOf('A') → "A"
String to char	string.charAt(index)	"Hello".charAt(0) → 'H'
char to int	(int) c	(int) 'A' → 65
int to char	(char) i	(char) 65 → 'A'
Upper/Lower Case Conversion	Character.toUpperCase(c) / toLowerCase(c)	Character.toLowerCase('A') → 'a'

Wrapper Class Character

The Character class provides utilities for working with char.

Key Features:

1. Constants:

   • Character.MIN_VALUE: '\u0000'.

   • Character.MAX_VALUE: '\uffff'.

2. Static Methods:

   • Character.isDigit(char c): Checks if the character is a digit.

   • Character.isLetter(char c): Checks if the character is a letter.

   • Character.isUpperCase(char c): Checks if it’s uppercase.

   • Character.isWhitespace(char c): Checks if it’s a whitespace character.

Common Mistakes

1. Using Strings Instead of char:

   • 'A' (char) ≠ "A" (String).

2. Casting Beyond Valid Range: Casting large integers to char can lead to unexpected results due to wrapping.

3. Treating char as Boolean: Avoid using characters like 'Y' or 'N' as substitutes for true/false

Examples

Basic example

char letter = 'A';
char digit = '5';
char symbol = '#';

System.out.println("Letter: " + letter);
System.out.println("Digit: " + digit);
System.out.println("Symbol: " + symbol);

// Arithmetic operation
System.out.println("Next letter: " + (char) (letter + 1)); // 'B'

Using char with Loops

public class CharLoopExample {
    public static void main(String[] args) {
        for (char c = 'A'; c <= 'Z'; c++) {
            System.out.print(c + " ");
        }
    }
}

Working with Unicode Characters

public class UnicodeExample {
    public static void main(String[] args) {
        char smiley = '\u263A'; // Unicode for ☺
        System.out.println("Smiley: " + smiley);
    }
}

Using char in Arrays

public class CharArrayExample {
    public static void main(String[] args) {
        char[] vowels = {'A', 'E', 'I', 'O', 'U'};

        for (char vowel : vowels) {
            System.out.println(vowel);
        }
    }
}

String Manipulation with char

public class StringCharExample {
    public static void main(String[] args) {
        String name = "Hello";
        char firstChar = name.charAt(0);
        System.out.println("First Character: " + firstChar);
    }
}

Using char with Streams

import java.util.stream.IntStream;

public class CharStreamExample {
    public static void main(String[] args) {
        String text = "Hello World";
        text.chars()
            .mapToObj(c -> (char) c)
            .forEach(System.out::println);
    }
}

Custom Character Validation

public class CharValidation {
    public static void main(String[] args) {
        char c = '9';

        if (Character.isDigit(c)) {
            System.out.println(c + " is a digit.");
        } else if (Character.isLetter(c)) {
            System.out.println(c + " is a letter.");
        } else {
            System.out.println(c + " is neither a digit nor a letter.");
        }
    }
}