CSIS 110 - Lecture 16
User Input
Java provides a Library class that we can use to get user input from a text window. This
class is called Scanner.
Before we can use the Scanner class, we need to import it (java.util.Scanner).
We can construct a new Scanner object and associate it with the keyboard:
Scanner stdin = new Scanner( System.in );
(stdin – standard input device)
The Scanner class contains the following methods:
String nextLine() – read from the Scanner up to the return key
Int nextInt() – read an int from the Scanner. An error occurs if the next item is not an int.
double nextDouble()
boolean nextBoolean()
boolean hasNext() – returns true if there is data available in the Scanner.
Let's try to write some code that gets an int from the user.
The String class
We've seen lots of Strings. The String class includes lots of methods. What methods have
we already seen in this class?
length()
equals()
Here are some more:
charAt( int index ) – return the character at the given index in the String. What
is the valid range of indices? Examples: String s = "Hello world!". How do I
extract the first character? The fourth character? The last character?
indexOf( char c ) – return the index of the first occurrence of the character in the
String. What is s.indexOf( 'w' )? How about s.indexOf( 'l' ); How
about s.indexOf( 'b' );
How about s.indexOf( 'L' );
lastIndexOf( char c ) – return the index of the last occurrence of the character
