Question

Assume the following variable declaration exists in a program: Int number \(=123456\) Write a statement that uses system.out.printf to display the value of the number variable in a field that is 10 spaces wide, with comma separators.

Short answer

Answer: The output will be " 123,456" where there are 3 leading spaces, providing a total width of 10 spaces with a comma separator.

Step-by-step solution

Understand the number format

We have an integer variable "number" which contains the value 123456. We need to display it in the specified format that is 10 spaces wide and with comma separators.

Start with System.out.printf method

To display the value in the specified format, we need to use the "System.out.printf" method in Java. The general syntax is: System.out.printf("format_specification", variable); where "format_specification" defines how the variable needs to be formatted.

Create the format specification

We need to create the format specification string that tells how the number should be formatted. Following are the required constraints: - % indicates that we will use a format specifier for a variable - 10 specifies the width of the field (10 spaces wide) - , indicates that we want to use a comma separator (for thousands) - d specifies that our variable is an integer Combining these constraints, our format specification string will be: "%,10d"

Writing the complete Java statement

Now, we have the format specification, we can write the complete Java statement to print the desired output using System.out.printf: System.out.printf("%,10d", number); This single line of code will display the value of "number" in a field that is 10 spaces wide, with comma separators.

Key concepts

Java Formatting

Java provides several ways to format output so it can be displayed in a more readable or presentable form. This feature is fundamental when representing data in user interfaces or when output needs to meet certain stylistic or structural standards.

One can format numbers, strings, dates, and more using various formatting methods available in Java. The idea is to convert raw data into a human-friendly format. Formatting is not just about adding style; it also provides clarity, by making information easier to parse, especially when dealing with large quantities or lengthy text.

When it comes to formatting output in Java, there are a few key tools and classes to be aware of, such as java.text.Format, java.text.MessageFormat, java.text.NumberFormat, and java.text.SimpleDateFormat. Each serves its own purpose depending on whether you are formatting general text, numbers, or dates.

Printf Method

The printf method is a powerful feature of Java's PrintStream class, which enables formatted output. It stands for 'print format' and is reminiscent of the C language's printf function. The method is convenient for displaying data in a structured manner, and it uses a format string that contains text and format specifiers.

Format specifiers begin with a percent symbol (%) and denote the type of data and its presentation. For example, %d for integers, %f for floating-point numbers, and %s for strings. Modifiers can be inserted between the percent symbol and the type-specific character to control minimum width, precision, and other aspects of formatting.

One powerful aspect of printf is its support for locale-sensitive formatting. By using format specifiers, one can display numbers with specific cultural number separators, as in the exercise solution where a comma is used for thousands grouping. To print text following specific formatting, proper understanding and usage of these specifiers are crucial.

Numeric Output Formatting

Numeric output formatting deals with displaying numbers in a manner that is both readable and compliant with the desired output structure. In Java, numbers can be formatted to show a fixed number of decimal places, align to certain widths, or even display in scientific notation.

For integers, modifications like having leading zeros, adding comma separators, or aligning to the right or left within a certain width can make data much more digestible. For example, displaying a large number with comma separators helps in distinguishing thousands, millions, and so forth, which is often used in financial or engineering applications.

In the given exercise, formatting the integer requires it to be ten characters in width, aligning to the right, and displaying commas to separate thousands. The %,10d format specifier in the printf method addresses these needs. The decimal integer d is preceded by a comma, which inserts the thousand separators, and the number 10 provides the field width. Adequate control over such formatting details plays a significant role in creating user-friendly console applications and reports.