Lecture 6

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Reading Input and Scanner Class
• Scanner Class
• Reading Input
• Reading for this class: L&L, 2.6
Reading Input
• Programs generally need input on which to operate
• The Scanner class provides convenient methods
for reading input values of various types
• A Scanner object can be set up to read input from
various sources, including from the user typing the
values on the keyboard
• Keyboard input is represented by the System.in
object
Reading Input
• The following line creates a Scanner object that
reads from the keyboard:
Scanner scan = new Scanner (System.in);
• The new operator creates the Scanner object
• Once created, the Scanner object can be used
to invoke various input methods, such as:
answer = scan.nextLine();
Reading Input
• The Scanner class is part of the
java.util class library, and must be
imported into a program to be used
• See Echo.java (page 91)
• The nextLine method reads all of the
input until the end of the line is found
• The details of object creation and class
libraries are discussed further in Chapter 3
Input Tokens
• Unless specified otherwise, white space is used to
separate the elements (called tokens) of the input
• White space includes space characters, tabs, new line
characters
• The next method of the Scanner class reads the next
input token and returns it as a string
• Methods such as nextInt and nextDouble read data
of particular types
• See GasMileage.java (page 92)

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