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11
BASIC INPUT/OUTPUT
Learning Objectives
11.1 Input/Output in Java 11.2 The StringTokenizer Class
11.3 Introducing Streams 11.4 Operations on Files
The data entered through input devices or used in processing is temporarily stored in memory. Once we exit the
program or switch off our device, this data is lost. It sometimes becomes essential to permanently store input and
processed data for future reference. This is achieved by using files, which are considered the digital substitute for the
paper files used to preserve physical documents.
In this chapter, we will learn about the Scanner class and the Printer class. Next, the concept of the StringTokenizer
class will be introduced. Then, we will understand how to handle different types of files in Java including binary and
text files.
11.1 INPUT/OUTPUT IN JAVA
As you know that every program needs an input to process and generate an output. Every programming language
has specific keywords to accept data from the input device and to display results on the output device. Java provides
Scanner and PrintStream classes to handle input and output operations respectively. Let us learn about these classes
in detail.
11.1.1 The Scanner Class
This is a revision tour of the Scanner class which is already discussed in Chapter 5 of this book. The Scanner class is used
to read input from the keyboard for primitive data types including int, float, double, char, etc. It can also read input for
non-primitive data types like String, File, InputStream(System.in) and similar classes that can execute the interfaces.
The Scanner class is defined in java.util package. So, while using the Scanner class in a program, we have to import it
by using the following statement:
java.util.*;
OR
java.util.Scanner;
Each individual piece of data in the Scanner class is called a token. The tokens are separated by characters called
delimiters. The default delimiter is whitespace, though any character can be used as a delimiter.
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