Lecture 8Using casts, Strings and WordUtil

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

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)

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

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)

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");}

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 )

Remember the 3 Different Kinds of Classes ?

1. Application Class – what we've been doing– Has public static void main ( String [] args)

2. Instantiable Class – use to make objects from– String, Scanner

3. Classes with only static utility methods – like Math class

WordUtil class – another class with static utility methods

• How to get the 15th word?

• How to check if a word is in the dictionary?