Java Data Types

1. Java Data Types Characters and Unicode

2. Unicode Characters, like the letters of the alphabet and other printable symbols, are represented internally in the computer by a numerical code. The coding system that Java relies on for characters is called Unicode. Unicode assigns an integer value to each separate printable character. Unicode is based in part on a previous coding system known as ASCII.

3. Unicode • Though Unicode handles thousands of characters, this will only cover the first 128 codes. • English alphabet • Keyboard symbols • Codes that don’t represent printable characters

4. Control codes The first 32 codes are non-printable control codes. They are referred to as control codes because they originated as instructions for communicating with or controlling a device. Most of these codes are of no use to the programmer. But there are some, such as the line feed and carriage return codes, which may be useful for printed output.

5. Control codes System.out.print(“\n”); The escape sequence “\n” causes the pair of control codes, line feed and carriage return, to be generated. Similarly, “\t” causes a horizontal tab to be generated. Although not literally printable, these characters can affect the appearance of the output.

6. Control codes

7. Unicode characters The Unicode values from 32 to 127 are printable, except for code 127, which stands for deletion. The letters of the alphabet, small and capital, and the various punctuation marks are arranged as they are for historical reasons. The sort order for characters or text items is based on their Unicode values.

8. Unicode characters

9. New data type: char We can now consider the character type, char. ‘char’ is effectively an integer type. It is possible to cast between something typed char and something typed int. The underlying value is always an integer. The type (int or char) determines whether the integer value or the associated Unicode character is displayed. The following program illustrates the idea that an integer can be cast to a character and printed out as such.

10. Char public class UnicodeChars{ public static void main(String[] args) { char myChar;inti; i = 65;myChar = (char) i;System.out.println(myChar); //Prints A }}

11. Char • In this program, the char type takes the integer value of 65, and finds the character associated with it, capital letter A. • It isn’t always necessary to use a number to assign a value to a char type. You can directly set the character you want. • myChar = ‘A’; • Note that we use single quotes instead of double quotes to denote a single character value. Double quotes signify a string, while single quotes signify a character.

12. Finding the integer value of a char • It is also possible to find the integer value of a char type, by casting it to an int, as shown below: • Char myChar = ‘A’;int i = (int) myChar;System.out.println(i); //Prints 65

13. Lab • Prepare yourselves! You are now ready for questions 39 to 42 on the assignment sheet. • The first couple of questions consists of determining a character from an integer, and an integer from a character. • The last couple will involve taking an integer/char type, and turning it into the other type.