Question

Write the header for a method named distance. The method should return a double and have two double parameter variables: rate and time.

Short answer

Based on the given step-by-step solution, provide a brief answer to the problem: The method header for the required function is `double distance(double rate, double time)`.

Step-by-step solution

Identify the return type

The method should return a double value representing the calculated distance. Therefore, the return type of the method will be "double".

Choose a method name

The exercise requires us to name the method "distance". So we will use this as our method name.

Define the input parameters

The method should have two double parameter variables: rate and time. We will include these parameters inside the parentheses following the method name.

Write the method header

Now we have all the required information to write the method header. The header will be: `double distance(double rate, double time)`

Key concepts

Double Return Type

In Java, methods can return various types of data, and it's crucial for programmers to specify the type of value that a method will return. The double return type is used when a method requires to return a decimal number with a potential for many digits of precision, which is common in calculations involving measurements or financial transactions.

Consider the double type as a container that can hold not just whole numbers, but fractions as well, making it ideal for representing values such as distance, which can be intricately exact. In our exercise, we conclude that the method named distance is intended to calculate and return the distance covered, likely based on the rate of speed and time traveled, hence the return type is appropriately designated as double.

Let's illustrate with an easy example:

• If rate is 60.5 (km/h) and time is 1.5 (h), our distance method should return a double value which could be 90.75 (km).

This accuracy is possible because of the double return type's ability to handle decimal numbers.

Parameter Variables

Parameter variables, commonly known as parameters, are the variable placeholders that accept values when a method is called. They are essential to the functionality of a method as they allow the passage of information to a method. In the context of this exercise, we have two double parameter variables: rate and time.

When defining a method, it is essential to specify the type of each parameter variable, because it determines what kind of values the method can accept. Each parameter is separated by a comma within the method header.

Using parameters provides flexibility to our distance method:

• They allow calculation of the distance for various rates and times.
• They can be used to dynamically change the behavior of the method on different invocations.

It's as if we’re telling Java: 'Hey, please prepare to receive two double values when someone calls the distance method, and I will use these values to calculate something important!' That's precisely what we are doing when we define the parameters in the method header.

Method Signature

The term method signature in Java refers to the part of the method declaration that includes the method name and the parameter list. It's a key concept in Java because the method signature is what the Java runtime uses to differentiate between methods when they are called or overloaded.

In our exercise, the method signature is distance(double rate, double time). It encompasses two crucial pieces of information: the name of the method, which is distance, and the types and order of parameters, which in this case are two double numbers named rate and time. It does not include the return type.

The uniqueness of a method signature is vital because it allows Java to understand which method to call in case multiple methods have the same name but different parameters (a concept known as method overloading). For instance, if we were to add another method signature like distance(int steps, int stepLength), Java would treat it as an entirely separate method due to its distinct signature, despite having the same name.