Reference types - Data Structures and Problem Solving Using Java - page 56

figure 2.18
Read exactly two
integers from the
same line and output
maximum using two
Scanner s

1 class MaxTestD
2 {
3 public static void main( String [ ] args )
4 {
5 Scanner in = new Scanner( System.in );
6
7 System.out.println( "Enter 2 ints on one line: " );
8 try
9 {
10 String oneLine = in.nextLine( );
11 Scanner str = new Scanner( oneLine );
12
13 int x = str.nextInt( );
14 int y = str.nextInt( );
15
16 if( !str.hasNext( ) )
17 System.out.println( "Max: " + Math.max( x, y ) );
18 else
19 System.err.println( "Error: extraneous data on the line." );
20 }
21 catch( NoSuchElementException e )
22 { System.err.println( "Error: need two ints" ); }
23 }
24 }

integers (lines 15 and 16). If anything goes wrong, a NoSuchElementException
will be handled.
The use of the second Scanner in Figure 2.17 can work well and is conve-
nient; however, if it is important to ensure that there are no more than two
integers per line, we would need additional code. In particular, we would need
to add a call to str.hasNext () , and if it returned true, we would know that
there is a problem. This is illustrated in Figure 2.18. There are other options,
such as the split method in String , as described in the exercises.

2.6.3 sequential files

One of the basic rules of Java is that what works for terminal I/O also works
for files. To deal with a file, we do not construct a BufferedReader object from
an InputStreamReader . Instead, we construct it from a FileReader object, which
itself can be constructed by providing a filename.
An example that illustrates these basic ideas is shown in Figure 2.19.
Here, we have a program that will list the contents of the text files that are
specified as command-line arguments. The main routine simply steps
through the command-line arguments, passing each one to listFile . In

FileReader is used
for file input.