Question

Write Java statements that accomplish each of the following tasks: a) Display the message "Enter an integer: ", leaving the cursor on the same line. b) Assign the product of variables b and c to variable a. c) State that a program performs a sample payroll calculation (i.e., use text that helps to document a program).

Short answer

Use `System.out.print`, `a = b * c;` and comments for documentation.

Step-by-step solution

Displaying a message

To display the message 'Enter an integer: ' and leave the cursor on the same line, use the `System.out.print` method in Java. This will not move the cursor to a new line after displaying the message. ```java System.out.print("Enter an integer: "); ```

Assigning the product to a variable

To assign the product of variables `b` and `c` to variable `a`, use the assignment operator `=` along with the multiplication operator `*`. Assuming variables `b` and `c` are already defined: ```java a = b * c; ```

Adding a comment for documentation

To state that the program performs a sample payroll calculation, you should add a comment in the code. Comments in Java are written with `//` for single-line comments. ```java // This program performs a sample payroll calculation ```

Key concepts

Java input/output

The process of handling input and output in Java is foundational. It's essential for interacting with users and obtaining or showcasing data. Java uses the `System.out` object to produce output. The `System.out.print` method is particularly useful when you want to display text without moving the cursor to the next line.

For example, when prompting a user to "Enter an integer: ", using `System.out.print` displays the text, keeping the user on the same line to input information. This creates a more seamless interaction, especially in console applications. Here’s a brief look at the different methods:

• `System.out.print`: Displays text and keeps the cursor on the same line.
• `System.out.println`: Outputs text and moves the cursor to the next line.
• `System.out.printf`: Allows formatted output, similar to the `printf` function in other languages like C.

Effective use of these commands helps in creating a smooth user experience in Java applications.

Java variables

In Java, variables are containers for storing data values. To use a variable, you need to declare it, specifying the type of data it will hold. This is crucial because Java is a statically-typed language, meaning that the type of a variable must be known at compile time.

A statement such as `int a;` declares a variable `a` that can store integers. In our example, the task is to assign the product of variables `b` and `c` to variable `a`, which follows these steps:

• Ensure that variables `b` and `c` are already declared and initialized (e.g., `int b = 5, c = 10;`).
• Use the assignment operator to assign the result of the expression `b * c` to `a`: `a = b * c;`.

By understanding how to declare and utilize variables, you can efficiently handle data within your Java programs. This is a key step in performing calculations and storing results effectively.

Java comments

Comments are an integral part of programming that helps in documenting the code. They make complex code understandable and maintainable. In Java, comments can be single-line or multi-line, serving different purposes.

When you want to describe a particular piece of code, a single-line comment using `//` is sufficient. For example, the line `// This program performs a sample payroll calculation` adds clarity to the subsequent code. It tells any developer or user reviewing the code what purpose it serves, without executing as code.

For describing larger sections, multi-line comments are helpful:

• Single-line comments: `// comment text`
• Multi-line comments: `/* comment block */`

Comments are ignored by the Java compiler, serving purely as a developer note. They should be used wisely to enhance code readability, which is crucial for effective collaboration and future code reviews.