Question

Assuming that x = 2 and y = 3, what does each of the following statements display? a) System.out.printf("x = %d%n", x); b) System.out.printf("Value of %d + %d is %d%n", x, x, (x + x)); c) System.out.printf("x ="); d) System.out.printf("%d = %d%n", (x + y), (y + x));

Short answer

'a' displays 'x = 2', 'b' displays 'Value of 2 + 2 is 4', 'c' displays 'x =', and 'd' displays '5 = 5'.

Step-by-step solution

Analyzing Statement a

Statement a is a Java printf statement that uses a format specifier '%d' to output an integer value, followed by '%n' to produce a new line. The variable 'x' holds the value 2, so it will display 'x = 2' followed by a new line.

Analyzing Statement b

Statement b uses three format specifiers, '%d', and one operation inside the arguments (x + x). Given that x is 2, the operation inside the arguments will evaluate to 4. So, the output will be 'Value of 2 + 2 is 4' followed by a new line.

Analyzing Statement c

Statement c does not have a format specifier or a new line character. It simply displays the string 'x =', without a subsequent value or new line.

Analyzing Statement d

Statement d uses two format specifiers '%d' to output the result of two operations: (x + y) and (y + x). As x is 2 and y is 3, both operations result in 5. The output is '5 = 5' followed by a new line.

Key concepts

Format Specifiers

When it comes to displaying information in Java, format specifiers are essentially 'placeholders' that tell the printf method what type of data to expect and how to display it. For example, in the provided exercise, %d is a format specifier used to indicate that an integer value is going to be inserted into that spot in the string.

There are several types of format specifiers available in Java for different data types:

• %s for strings
• %d for decimal integers
• %f for floating-point numbers
• %t for date/time values

Each format specifier can be customized with flags, width, precision, and conversion characters to further refine the output, like controlling the number of decimal places for a float or padding a number with zeros.

Output Statements

Output statements in Java are used to communicate with the user by sending text to the console or another output destination. The System.out.printf method, an output statement used in the exercise, stands for 'print format' and enables formatted output. Unlike System.out.println, which merely prints a string followed by a newline, printf can format the string through format specifiers.

Here's a closer look at the output statements provided:

• Statement a includes a newline character (%n), ensuring that anything printed afterward starts on a new line.
• In statement b, we see that printf can also accept expressions like (x + x), which are evaluated first before being printed.
• Statement c shows that not all output statements require format specifiers; plain text can be printed as-is.
• Statement d exemplifies that the same format specifier can be used multiple times within the same statement and will be replaced sequentially by the provided arguments.

The systematic use of these output statements helps in distributing information in a structured and predictable format.

String Formatting

String formatting in Java is a powerful way to control the appearance of text output. With the printf method, you're not just sending characters to the console; you're crafting a template with specific placeholders, which format specifiers fill dynamically. This approach is quite flexible and useful for creating easily readable and properly aligned text.

For instance, imagine needing to display a table of numbers where each column aligns correctly; format specifiers can handle this with ease. In addition, string formatting allows for the localization of output, adapting it to various languages and regions, which is crucial in global applications.

Overall, string formatting with the printf method combines the raw data with a specified format to create a polished, final output that enhances the readability and usability of the information presented to the user.