Lecture 8 Using casts, Strings and WordUtil

1. Lecture 8Using casts, Strings and WordUtil

2. Agenda • Generating random numbers • Casts • Casting a double into an int • Casting an int into a char • Casting a char into an int • Strings again • reading a String • checking the length of a String • can we cast a String into an int? • Or an int to a String? • Using the WordUtil class

3. Generating Random Numbers • Recall Lab2 the Math.random() method: • double myNumber; • myNumber = Math.random(); // (from 0 to .999) • Then in Lab5: • double secret; • secret = Math.round(Math.random()*100); • 0 to 100 ( 0 and 100 come up half as often as others) • OR secret = (int)( Math.random()*100); • 0 to 99 ( evenly distributed)

4. A Cast "filters" a value into a different type • int x = (int) 4.1243; // x gets 4 • double z = 56.23; • int y = (int) z; // y gets 56, z remains 56.23 • z = (double) y; // z gets 56.0 • char letter = 'c'; • int code = (int) letter; // code gets 97 • letter = (char) 65; // letter gets 'A' • letter = 'A'; // this is more clear, same value

6. For this lab • We'll use casts to convert a random double to int • int num = (int)( Math.random()*100); • 0 to 99 ( evenly distributed)

7. String class • Create a String: • String word; • word = "hello"; • Read a String • word = in.next(); // in is a Scanner object • Compare 2 strings • if ( word.equals("hello")) { ...println("good morning"); }

8. How long is a String • Print the length: • ...println("length of word = " + word.length() ); • Check if the length is 5 letters: • if ( word.length() == 5 )

9. Remember the 3 Different Kinds of Classes ? • Application Class – what we've been doing • Has public static void main ( String [] args) • Instantiable Class – use to make objects from • String, Scanner • Classes with only static utility methods • like Math class

10. WordUtilclass – another class with static utility methods • How to get the 15th word? • How to check if a word is in the dictionary?