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We introduced the body mass index (BMI) calculator in Exercise 1.10. The formulas for calculating BMI are $$B M I=\frac{\text {weightInPounds} \times 703}{\text {heightInInches} \times \text {heightInInches}}$$ or $$B M I=\frac{\text {weightln Kilograms}}{\text {height} \text {InMeters} \times \text {height} \text {InMeters}}$$ Create a BMI calculator that reads the user鈥檚 weight in pounds and height in inches (or, if you prefer, the user鈥檚 weight in kilograms and height in meters), then calculates and displays the user鈥檚 body mass index. Also, display the following information from the Department of Health and Human Services/National Institutes of Health so the user can evaluate his/her BMI: [Note: In this chapter, you learned to use the int type to represent whole numbers. The BMI calculations when done with int values will both produce whole-number results. In Chapter 3 you鈥檒l learn to use the double type to represent numbers with decimal points. When the BMI calculations are performed with doubles, they鈥檒l both produce numbers with decimal points鈥攖hese are called 鈥渇loating-point鈥� numbers.]

Step by step solution

01

Prompt for User Input

Ask the user to input their weight in pounds and height in inches. Alternatively, if using the metric system, request their weight in kilograms and height in meters.

02

Read User Input

Use a programming statement to read the weight and height information provided by the user.

03

Convert Input to Correct Data Type

Ensure that the inputted weight and height are cast to the correct data type (e.g., 'int' for whole numbers in Chapter 1.10 or 'double' for floating-point numbers as will be learned in Chapter 3).

04

Calculate BMI

Using the appropriate formula, calculate the BMI. If the input is in pounds and inches, use the formula: \(BMI = \frac{\text{weightInPounds} \times 703}{\text{heightInInches}^2}\). If the input is in kilograms and meters, use: \(BMI = \frac{\text{weightInKilograms}}{\text{heightInMeters}^2}\).

05

Display BMI Result

Show the calculated BMI to the user.

06

Provide BMI Evaluation Information

Display the BMI categories from the Department of Health and Human Services/National Institutes of Health to help the user evaluate their BMI: Underweight = <18.5; Normal weight = 18.5鈥�24.9; Overweight = 25鈥�29.9; Obesity = BMI of 30 or greater.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Programming Exercise Solution

Creating a Body Mass Index (BMI) calculator in Java can be a great way to apply basic programming skills. A BMI calculator reads a user's weight and height, then calculates their BMI which is a measure of body fat based on these metrics. In Java, this involves several programming concepts such as user input handling, data type conversion, arithmetic operations, and conditional logic to display health evaluation information.

In solving this programming exercise, steps include prompting the user for input, reading the input, handling potential data type conversion, performing the BMI calculation, and finally displaying the results alongside relevant health information. This process not only teaches basic syntax and operations in Java but also emphasizes practical application by creating a tool that can provide valuable health-related insights.

BMI Calculation Formula

The Body Mass Index is calculated using a simple formula. For those using the imperial system, the BMI is calculated by multiplying the weight in pounds by 703 and then dividing it by the square of the height in inches, as shown by the formula: \[ BMI = \frac{\text{weightInPounds} \times 703}{\text{heightInInches}^2} \].

Alternatively, using the metric system, the weight in kilograms is divided by the square of the height in meters: \[ BMI = \frac{\text{weightInKilograms}}{\text{heightInMeters}^2} \]. It鈥檚 crucial to accurately convert these measurements and perform the arithmetic to ensure a correct BMI calculation.

User Input Handling

User input handling is an essential part of many programming exercises, including the BMI calculator. In Java, user input can be handled using a Scanner object which reads input from various sources like the keyboard. For a BMI calculator, you want to ensure you prompt the user clearly for their weight and height and then use the Scanner to capture this information.

It's vital to guide the user with precise instructions so they know what data to input and in what format, as this will affect the accuracy of the BMI calculation. Handling user input correctly can be the difference between a smoothly running program and one that frequently encounters input-related errors.

Data Type Conversion

When users input their weight and height, it鈥檚 initially received as a string which needs to be converted to the correct numerical data type. In early chapters of a programming textbook, integers ('int') are used for simplicity. However, to get a more accurate result, floating-point numbers ('double') are introduced later on.

For the BMI calculation, converting string input to 'int' will give a whole number result, while converting to 'double' allows for a fractional result which is more precise. Understanding how and when to convert data types is important for ensuring that your calculations are accurate and meaningful.

Health Evaluation Information

Once the BMI is calculated, it's informative to provide the user with health evaluation information. This generally includes categories defined by health organizations to indicate whether an individual鈥檚 BMI falls within a range that is underweight, normal, overweight, or obese.

Here are the standard categories:

• Underweight = BMI of less than 18.5
• Normal weight = BMI between 18.5 and 24.9
• Overweight = BMI between 25 and 29.9
• Obese = BMI of 30 or greater

Providing this information helps the user make better-informed decisions regarding their health and lifestyle changes if necessary. It's important for a BMI calculator to output not only the numeric BMI value but also this contextual information.