Keeping a running average of values in java

Question

I am trying to calculate the average of values given via repeated function calls.

Actually Bluej allows me to put the number to rate but if i am trying to put again it replaces the previous one, i want to be stored and after that an average to be shown.

I can't figure out how to do it

This is the part of code:

public int getRate() // here i put an int number
{
    return this.rate;
}

public void setRate(int rate) // here i change it but i think i don't need it
{
    this.rate = rate;
}

I can't use strange or complex commands because i am allowed to only use this type of commands like get/set and arraylists.

It is a school assignment.

Thanks

You need to provide more information. Where are the numbers coming from? An given object usually only holds one value for a field. And most times, set will change that value. — WJS, Apr 01 '22 at 18:18
Hi there, you might need to clarify what your goal is here and show the intended use case of this code - it's unclear exactly how you receive the values you want to calculate an average of. Do you want to record every time 'setRate' is called and calculate an average of given rates? — Ethan McTague, Apr 01 '22 at 18:18
@EthanMcTague yes exactly, i want to record every getRate and calculate the average between them. So, the when i put into getRate a number needs to be stored — Rares, Apr 01 '22 at 18:21

score 1 · Accepted Answer · answered Apr 01 '22 at 18:24

An easy way to keep an average of inputs is to keep track of:

The sum of all inputs received so far.
The number of inputs you have received.

Every time you call setRate to update the rate, you add to the sum and increment the count. You also need a special case for when no rates have been added yet, to avoid division by zero:

private int ratesSum = 0;
private int rateCount = 0;

public int getRate()
{
    return this.rate;
}

public void setRate(int rate)
{
    this.rate = rate;
    this.ratesSum += rate;
    this.rateCount++;
}

// Gets the average of all rates so far, or returns zero if no rates
// have been set yet.
public float getAverageRate()
{
    // Do not divide by zero
    if (rateCount == 0) return 0;

    return ((float)ratesSum) / ((float)rateCount);
}

Keeping a running average of values in java

1 Answers1