INTRODUCTION TO OBJECTS AND INPUT/OUTPUT - Java Programming: From Problem Analysis to Program Design - page 129

In this expression, we want to determine whether the substring in str2 starting at
position 17 and of length 4 is the same as the substring in str4 starting at position 9
and of length 4 . This expression returns true because these substrings are the same.
The program Ch3_SomeStringMethods.java , which shows the effect of the preceding
statements, can be found in the Additional Student Files folder at www.cengagebrain.com.

3

To summarize the preceding discussion of the class String :
1. String variables are reference variables.
2. A string object is an instance of the class String .
3. The class String contains various methods to process strings.
4. A String variable invokes a String method using the dot operator, the
method name, and the set of arguments (if any) required by the method.

Input/Output
A program performs three basic operations: it gets data into the program, it manipulates the
data, and it outputs the results. In Chapter 2, you learned how to manipulate numeric data
using arithmetic operations. Because writing programs for input/output (I/O) is quite
complex, Java offers extensive support for I/O operations by providing a substantial number
of I/O classes, such as the class Scanner . In the remainder of this chapter, you will:
￿ Learn how to format output using the method printf .
￿ Learn other ways to input data and output results in Java.
￿ Learn how to format the output of decimal numbers to a specific number
of decimal places.
￿ Learn how to instruct the program to read data from, or write output to,
a file. If there is a large amount of data, inputting data from the keyboard
every time you execute your program is not practical. Similarly, if the
output is large or you want to save the output for later use, you must save
a program's output to a file.

Formatting Output with printf
In Chapter 2, you learned how to show the output of a program on the standard output
device using the standard output object System.out and the methods print and
println . More specifically, to output the results, you used statements such as
System.out.print(expression) and/or System.out.println(expression) ,
where expression is evaluated and its value is output. However, the methods print
and println cannot directly format certain outputs in a specific manner. For example, the
default output of floating-point numbers is typically up to 6 decimal places for float