The primitive data type char

Review:
A computer can only store (binary) numbers

Non-numeric information (e.g.: letters) can be represented using a code
The char data type in Java:
char data type represents a single character

The Unicode is used as the standard representation method for characters
A Unicode character chart can be found here:
Some interesting character codes within the Unicode:

Defining and using char typed variables

Syntax to define a char typed variable:

char variableName; // The value (= number) in variable will be // interpreted as an Unicode

Example:

public static void main(String[] args) { char letter = 'A'; // Will store 65 in variable System.out.println( letter ); letter = 65; // Will store 65 in variable System.out.println( letter ); letter = 946; // 946 = Unicode for Greek letter beta System.out.println( letter ); letter = 24373; // My Chinese name System.out.println( letter ); }

DEMO: demo/04-Math+String/02-char/Intro.java

Size of Java's primitive data types

The memory cells used to store variables of primitive types:

Data type # Bytes ------------------------------------------ double 8 bytes float 4 bits long 8 bytes int 4 bytes short 2 bytes byte 1 byte char 2 bytes boolean 1 byte

A char typed variable contains an integer of 2 bytes or 16 bits

How are char symbols stored inside the computer ?

Remember:
Everything stored inside the computer (memory) is a (binary) number
A character is:
A (binary) number where the computer is "told" to interprete the number using the Unicode table.

Example:

public static void main(String[] args) { char x = 65; // Interprete number with Unicode System.out.println( x ); int y = 65; // Interprete number as binary number System.out.println( y ); }

DEMO: demo/04-Math+String/02-char/Typing.java

Computations with char data

You can perform arithmetic operations on char typed values

Example: get the next letter:

public class NextChar { public static void main(String[] args) { char c = 65; // 'A' System.out.println(c); // Print 'A' System.out.println( (int) c ); // Tell Java to print c as an int c = (char) (c + 1); // Add 1 to c System.out.println(c); // Prints 'B' System.out.println( (int) c ); // Tell Java to print c as an int } }

DEMO: demo/04-Math+String/02-char/NextChar.java

Bit of history: char in older programming languages...

Java was invented in 1995 and it's a pretty recent programming language
Older programming languages (such as C, C++) were invented before the Unicode:

The ASCII code:

The ASCII code is an 8 bits code
(Unicode is a 16 bits code)
The ASCII code only represent the English alphbet
The ASCII code is a subset (= contained by) the Unicode

Using the Unicode numbers

Unicode for some commonly used characters:

Characters Code value in decimal Unicode value -------------------------------------------------------------------- '0' '1' .. '9' 48 49 .. 57 \u0030 \u0031 .. \u0039 'A' 'B' .. 'Z' 65 66 .. 90 \u0041 \u0042 .. \u005A 'a' 'b' .. 'z' 97 98 .. 122 \u0061 \u0062 .. \u007A

You can use any one of these expressions to represent the character '0' in Java:

'0' (preferred) 48 '\u0030'

Example:

char c; c = '0'; // '0' preferred ! c = 48; // '0' c = '\u0030'; // '0'

DEMO: demo/04-Math+String/02-char/Unicode.java

Special chacters: '\t' and '\n'

The backslash (\) character is used in Java to denote some characters with special effects

Some commonly used characters that have special effect on the terminal:

Character symbol Code in decimal Name of character ------------------------------------------------------------- '\t' 9 TAB '\n' 10 Newline

Example:

System.out.print('a'); System.out.print('\t'); System.out.print('c'); Output: a c

DEMO: demo/04-Math+String/02-char/Tab.java