This question involves the implementation of a fitness tracking system that is represented by the StepTracker class. A StepTracker object is created with a parameter that defines the minimum number of steps that must be taken for a day to be considered active. The StepTracker class provides a constructor and the following methods.
Days with at least 10,000 steps are considered active.Assume that the parameter is positive.
tr.activeDays();
0
No data have been recorded yet.
tr.averageSteps();
0.0
When no step data have been recorded, the averageSteps method returns 0.0.
tr.addDailySteps(9000);
This is too few steps for the day to be considered active.
tr.addDailySteps(5000);
This is too few steps for the day to be considered active.
tr.activeDays();
0
No day had at least 10,000 steps.
tr.averageSteps();
7000.0
The average number of steps per day is (14000 / 2).
tr.addDailySteps(13000);
This represents an active day.
tr.activeDays();
1
Of the three days for which step data were entered, one day had at least 10,000 steps.
tr.averageSteps();
9000.0
The average number of steps per day is (27000 / 3).
tr.addDailySteps(23000);
This represents an active day.
tr.addDailySteps(1111);
This is too few steps for the day to be considered active.
tr.activeDays();
2
Of the five days for which step data were entered, two days had at least 10,000 steps.
tr.averageSteps();
10222.2
The average number of steps per day is (51111 / 5).
This question asks you to write the complete StepTracker class, including the constructor and any required instance variables and methods. Your implementation must meet all specifications and conform to the example.
Read through the problem statement and determine the instance variables required for this class. When starting to work on a problem like this it helps to circle the words that are important and may describe the instance variables.
Select the phrases below which probably mention an instance variable. Note that some of these may be referring to the same variable or to local variables.
Think about phrases that indicate a value that is being stored or changed or returned.
This question involves the implementation of a fitness tracking
system that is represented by the **StepTracker** class.A StepTracker object is created with a parameter that defines
the minimum number of steps that must be taken for a day to be considered active.The StepTracker class provides a constructor and
the following methods.
- addDailySteps, which accumulates information about steps,
in readings taken once per day.
- activeDays, which returns the number of active days.
- averageSteps, which returns the average number of steps per day,
calculated by dividing the total number of steps taken
by the number of days tracked.
Answering the multiple choice problem will help you determine the instance variables through the constructor parameters and accessor and mutator methods.
Given the StepTracker class description above, which of these statements describes an instance variable that the StepTracker constructor should set using a parameter?
Yes, addDailySteps(1000) is a mutator method that adds the steps given as a parameter to an instance variable that keeps track of the steps taken so far.
tr.activeDays();
No, activeDays() is an accessor method that returns the number of active days.
tr.averageSteps();
No, averageSteps() is a complex accessor method that calculates and returns the average number of steps from the instance variable.
At this point you should be able to answer the following questions: What are the instance variables (at least 4!) that you need for the StepTracker class? What are the data types for each instance variable?
Write the first draft of the class StepTracker below with the class name, the instance variables, and the constructor with a parameter for the minimum number of steps threshold for active days. Make sure it compiles.
This problem asks you to write a simple accessor method called activeDays which returns the number of active days (which should be an instance variable) for 1 point.
Accessor methods need a return type since they return the value of an instance variable or a value calculated from instance variables.
private void activeDays()
Accessor methods should not be private.
public int activeDays(int numSteps)
Accessor methods do not usually take parameters.
public void activeDays(int numSteps)
Accessor methods need a return type since they return the value of an instance variable or a value calculated from instance variables, and they do not usually have a parameter.
public int activeDays()
Correct, accessor methods are public, have a return type, and no parameter.
Copy the code from your first draft of the class StepTracker above with the instance variables and constructor. Write the accessor methods activeDays which returns the number of active days.
class Example
{
//Instance variable declaration
private typeOfVar varName;
// Mutator method template
public void changeVarName(typeOfVar newValue)
{
// an instance variable is changed through = or an operator like +=, -=, ++, etc.
varName = newValue;
}
}
Answering the multiple choice problem will help you determine the mutator method header.
The code for this mutator method is a little more complex than the template above, because it needs to change more than 1 instance variable. Notice the comments in the sample code execution:
Copy the code from your draft of the class StepTracker above with the class name, the instance variables, constructor, and accessory method. Write the mutator method addDailySteps which takes a parameter and adds it to the appropriate instance variable and changes other instance variables appropriately.
This problem asks you to write a more complex accessor method which uses the instance variables to calculate and return the averageSteps for 2 points. This method returns the average number of steps per day, calculated by dividing the total number of steps taken by the number of days tracked.
Accessor methods need a return type since they return the value of an instance variable or a value calculated from instance variables.
public int averageSteps()
When you compute an average using division, you usually end up with a double value, not int.
public double averageSteps()
Correct, accessor methods are public, have a return type, and no parameter. In this case, returning an average requires a double return type.
public void averageSteps(int numSteps)
Accessor methods need a return type since they return the value of an instance variable or a value calculated from instance variables, and they do not usually have a parameter.
The complex accessor method averageSteps() must calculate the average number of steps from your instance variables. Notice that the first time it is called in the sample code execution, it returns 0.0 since there are no steps recorded. This avoids a divide by 0 error.
When no step data have been recorded, the averageSteps method returns 0.0.
Checkpoint11.2.15.
Copy the code from your draft of the class StepTracker above with the instance variables, constructor, accessor and mutator methods. Write the accessor method averageSteps which returns the average number of steps per day, calculated by dividing the total number of steps taken by the number of days tracked.
