Data and Expressions - Java Software Solutions: Foundations of Program Design - page 89

called a constructor to set up the object. The Scanner constructor accepts a
parameter that indicates the source of the input. The System.in object represents
the standard input stream , which by default is the keyboard. Creating objects
using the new operator is discussed further in the next chapter.
Unless specified otherwise, a Scanner object assumes that white space charac-
ters (space characters, tabs, and new lines) are used to separate the elements of
the input, called tokens , from each other. These characters are called the input
delimiters . The set of delimiters can be changed if the input tokens are separated
by characters other than white space.
The next method of the Scanner class reads the next input token as a string
and returns it. Therefore, if the input consisted of a series of words separated by
spaces, each call to next would return the next word. The nextLine method reads
all of the input until the end of the line is found, and returns it as one string.
The program Echo , shown in Listing 2.8, simply reads a line of text typed by the
user, stores it in a variable that holds a character string, then echoes it back to the screen.
The import statement above the definition of the Echo class tells the program
that we will be using the Scanner class in this program. The Scanner class is
part of the java.util class library. The use of the import statement is discussed
further in Chapter 3.
Various Scanner methods such as nextInt and nextDouble are provided to
read data of particular types. The GasMileage program, shown in Listing 2.9,
reads the number of miles traveled as an integer, and the number of gallons of
fuel consumed as a double, then computes the gas mileage.
LISTING 2.8
//********************************************************************
// Echo.java Author: Lewis/Loftus
//
// Demonstrates the use of the nextLine method of the Scanner class
// to read a string from the user.
//********************************************************************
import java.util.Scanner;
public class Echo
{
//-----------------------------------------------------------------
// Reads a character string from the user and prints it.
//-----------------------------------------------------------------
public static void main (String[] args)