The Scanner Class and Formatting Output

1. The Scanner Class and Formatting Output Mr. Lupoli

2. Items you need before beginning • From Website • Scanner Class Quick Reference Ditto

3. Introduction • The scanner class is a STANDARDIZED class that uses different methods for READING in values from either the KEYBOARD or a FILE. • Before this addition, many java programmers created their own scanner class to accomplish the same task

4. Introduction (cont.) • Remember • Keyboard  System.in • File  New File ()

5. Important Information • Must import • Java.util.Scanner; • Scanner will ignore white spaces BEFORE a value, but BY DEFAULT will STOP: • At a white space (those not reading in a line) • At a ‘\n’ (those reading in a line)

6. Methods in Scanner class • Just remember to firstINDENTIFY what exactly you wish to read in and HOW you want to use it. • Remember a numeric value CAN be read in as a String!! • Methods in the class are broken down into two categories • next() (reads value) • hasNext() (checks that a value is present to read) • This SHOULD remind you of the INTERATOR methods!!

7. Methods in the Scanner class • Scanner Class Quick Reference • On website • Please note that there are MATCHING “hasNext” for each shown on the ditto. • There are other methods in the class that I will not cover • Except Delimiter

8. Changing the token delimiter • Can change the token delimiter to something other than whitespace • useDelimiter(String pattern) • pattern can be a simple string of characters such as “:” or “---“ or pattern can be a regular expression (regex pattern) for advanced matching • note, if using a character that has meaning in regex patterns, will have to put a “\” in front of the character

9. Changing the token delimiter • Commonly used regular expressions (can combine these with each other and text strings) • . (period) match any one character • .* match any number of characters, including none • \\s match a single whitespace character • \\s+ match 1 or more whitespace characters • [abc] match any one character contained within the brackets

10. Changing the token delimiter

11. Introduction to Output Formatting • Most of us are used to using System.out.println to display the data • Using “printf” can display AND format the output • Printf is a OLD C command used to display • Literally the same syntax! • A “placeholder” is used to determine the exact output of the variable

12. Placeholder • A placeholder is used WITHIN the string of text you wish to be displayed • that place holder will display the value given a certain format

13. Printf() • Simplest Example int grade1 = 80; char grade2 = ‘B’; String grade3 = “Passing”; System.out.printf(“Lupoli received a %d, or %c, or %s”, grade1, grade2, grade3); // those in red are the place holders // those in green are the actual variables • Notice that order or variables are important!

14. Placeholder “flags” • %c, %d, is NOT the full extent • the placeholder have flags that will change the format of the output • \n will be needed to end the line

15. printf() Quick Reference • Use the OTHER side of the Scanner Quick Reference • Placeholder flags • read what each do • NOTICE the syntax the placeholder must use

16. Thanks!! • Thanks all. • Contact me if you have any questions.

17. Sources • Students • Mike McCoy • Jordan Clark • Websites • http://java.sun.com/j2se/1.5.0/docs/api/ • Books • Problem Solving and Program Design in C • Hanly and Koffman