Question

Write a statement for each of the following: a) Print 1234 right justified in a 10 -digit field. b) Print 123.456789 in exponential notation with a sign \((+\text { or }-)\) and 3 digits of precision. c) Print 100 in octal form preceded by 0 d) Given a Calendar object calendar, print a date formatted as month/day/year (each with two digits). e) Given a Calendar object calendar, print a time for the 24 -hour clock as hour:minute: second (each with two digits) using argument index and conversion suffix characters for formatting time. f) Print 3.333333 with a sign \((+\text { or }-)\) in a field of 20 characters with a precision of 3

Short answer

Use format specifiers like `%10d`, `%+.3e`, `%#o`, `%tm/%td/%ty`, `%tH:%tM:%tS`, and `%+20.3f`. Each is tailored to specific formatting requirements for numbers and dates.

Step-by-step solution

Formatting for Right Justified Integer

To print the integer 1234 right justified in a 10-digit field, use the format specifier `%10d`. This will allocate a total of 10 spaces for the number and align it to the right. **Statement:** ```java System.out.printf("%10d", 1234); ```

Formatting for Exponential Notation

To print the number 123.456789 in exponential notation with a sign and 3 digits of precision, use the format specifier `%+.3e`. This specifies that the number should have a sign and display 3 digits after the decimal point. **Statement:** ```java System.out.printf("%+.3e", 123.456789); ```

Formatting for Octal Representation

To print the number 100 in octal form preceded by a zero, use the format specifier `%#o`. The `#` flag ensures the zero is added at the beginning of the octal number. **Statement:** ```java System.out.printf("%#o", 100); ```

Formatting Date from Calendar Object

Assuming the `Calendar` object is initialized with a date, to print the date in month/day/year format with two digits each, use the format specifiers `%tm`, `%td`, and `%ty`. **Statement:** ```java Calendar calendar = /* initialized Calendar object */; System.out.printf("%1$tm/%1$td/%1$ty", calendar); ```

Formatting Time from Calendar Object

To print time in 24-hour format with hour:minute:second each with two digits, use the format specifiers `%tH`, `%tM`, and `%tS`, with positional indexing. **Statement:** ```java System.out.printf("%1$tH:%1$tM:%1$tS", calendar); ```

Formatting for Signed Float with Precision

To print the floating-point number 3.333333 with a sign in a field of 20 characters with a precision of 3, use the format specifier `%+20.3f`. This will display the number with a sign, allocate 20 spaces, and round to 3 decimal places. **Statement:** ```java System.out.printf("%+20.3f", 3.333333); ```

Key concepts

string formatting

String formatting in Java is a method to manipulate how strings are printed or displayed. It allows developers to specify the format in a systematic way. Java provides different methods to format strings, most notably through the `String.format()` and `System.out.printf()` methods. These methods make use of format specifiers that control the arrangement of text and numerical values.

For example, if you want to print an integer, a string, and a floating number in a specific format, you can specify the way they should be arranged. This is incredibly useful for creating outputs that are consistent and tidy. String formatting is especially powerful when dealing with diverse types of data that need to conform to a particular display format, like dates, currency, and complex numbers. Mastering string formatting helps create user-friendly interfaces and reports in applications.

printf specifiers

Printf specifiers are little codes that Java’s formatting methods recognize and use to display data in a specified pattern. They begin with a `%` sign and are followed by a single character that maps to a specific data type.

Here are a few common specifiers:

• `%d` - used for integers
• `%f` - used for floating-point numbers
• `%e` - for numbers in exponential notation
• `%c` - represents a character
• `%s` - handles strings

Printf specifiers can also include flags, minimum width, and precision. For instance, `%10d` means a minimum width of 10 for an integer with right justification, while `%.3f` specifies a floating number with 3 decimal places.

These specifiers ensure that data appears in a human-readable and professional format. By using printf specifiers, developers can easily align numbers and text in tables or create well-structured console outputs. They provide an excellent way to visually organize information, especially when printed outputs are critical for understanding program behavior.

calendar date formatting

Calendar date formatting in Java involves the use of `printf` specifiers tailored specifically for date and time data types. This is useful when you want to represent dates as months, days, years, and times in a standard format. Java gives us `%t` format specifiers that handle date and time values.

Let's look at some specifiers useful in formatting dates:

• `%tm` - prints the month in two digits, e.g., 01 for January
• `%td` - prints the day of the month in two digits
• `%ty` - provides the last two digits of the year

A common use is in timestamping records or data logs, where clarity and accuracy are crucial. For example, you can format a `Calendar` object to display a date as "MM/DD/YY" by structuring your printf statement with these specifiers.

This type of formatting is helpful in many applications where the user needs a clear, structured date representation, such as in scheduling systems, reporting software, or any application that requires an accurate historical record.

exponential notation

Exponential notation in Java allows numbers to be formatted in a way that represents them as a power of 10. It's useful when dealing with extremely large or small floats, providing a concise and readable form. The printf specifier `%e` is used in Java to format numbers this way. It's especially handy in scientific calculations and when high precision is less critical than the display of scale.

For example, using `%+.3e` will represent a number with a sign, and three digits after the decimal, varying the scaling to make room for large values. This can turn `123.456789` into `+1.235e+02`, which stands for \( 1.235 \times 10^2 \).

It's important because it saves space and simplifies understanding when dealing with datasets including wide-ranging values. Exponential notation is essential in fields where data handling involves very small or very high magnitude numbers like finance, scientific research, and engineering fields.