Reference types - Data Structures and Problem Solving Using Java - page 53

As already mentioned, the print and println methods are used for for-
matted output. Any type can be converted to a String suitable for printing by
calling its toString method; in many cases, this is done automatically.
Unlike with C and C++, which have an enormous number of formatting
options, output in Java is done almost exclusively by String concatenation,
with no built-in formatting.

The predefined
streams are
System.in ,
System.out , and
System.err .

2.6.2 the Scanner type
The simplest method for reading formatted input is to use a Scanner . A Scanner
allows the user to read lines one at a time using nextLine , String s one at a time
using next , or primitive types one at a time using methods such as nextInt and
nextDouble . Prior to attempting to perform a read, it is customary to verify that
the read can succeed by using methods such as hasNextLine , hasNext , hasNextInt ,
and hasNextDouble , which yield boolean results; as such there is typically less
need to deal with exception handling. When using a Scanner it is customary to
provide the import directive

import java.util.Scanner;

To use a Scanner that reads from the standard input we must first construct
a Scanner object from System.in . This was illustrated in Figure 2.11 at line 7.
In Figure 2.11, we see that nextLine is used to read a String , and then the
String is converted to an int . From the discussion of Scanner in the previous
paragraph, we know there are several other options.
An alternative option, which is perhaps the cleanest, is the follow-
ing replacement, which avoids exceptions entirely, and uses nextInt and
hasNextInt :

System.out.println( "Enter an integer: " );
if( in.hasNextInt( ) )
{
x = in.nextInt( );
System.out.println( "Half of x is " + ( x / 2 ) );
}
else
{ System.out.println("Integer was not entered." }