Find the max value in local parameters

Question

I have 20 local parameters in a class and I want to know the efficient way to get the maximum value and total sum among all the parameters. Thank you in advance!

my code is something like

    public class EntityOfTheQuery{
    double value1;
    double value2;
    ...
    double value3;

    // this is the function I need 
    public void maxValue(){
    }
  }

Why don't you use an array? `double[] value = new double[20];`. Other than your options are limited. — Absurd-Mind, May 26 '14 at 12:20
If you can add the values in an array you can watch [this](http://stackoverflow.com/questions/16325168/how-would-i-find-the-maximum-value-in-an-array) — Paolo Forgia, May 26 '14 at 12:24
Find max or min in a a collection of objects it will be always O(n) in time even if you have not further informations about the collection. Therefore, no matter what approach you use because every element must be read and the cost is linear. — Emisilve86, May 26 '14 at 12:39

Kabulan0lak · Answer 1 · 2014-05-26T12:29:07.423

1

public double maxValue(){
    double[] a = {value1,value2,...,value20};
    List b = Arrays.asList(ArrayUtils.toObject(a));
    return Collections.max(b);
}

You could do it.

edited May 26 '14 at 12:29

answered May 26 '14 at 12:21

Kabulan0lak

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Math.max() is for two params not 20. – Deepu--Java May 26 '14 at 12:23
this will only work if you have all values in an array. But the OP asked for a method if all the values are properties of the class... – chresse May 26 '14 at 12:35
Nop, because I create the array from his 20 useless variables. – Kabulan0lak May 26 '14 at 12:37

score 0 · Answer 2 · answered May 26 '14 at 12:27

0

Take a array of size 20 instead of 20 different vars.

double[] value = new double[20];
public double maxValue(){
      Arrays.sort(value);
      return value[value.length-1];
    }

answered May 26 '14 at 12:27

Deepu--Java

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This is more work than necessary. You don't have to sort the whole array to find the min/max element. – Kenster May 26 '14 at 12:32
@Kenster There is no max min method for Arrays. – Deepu--Java May 26 '14 at 12:35
So? Finding the min/max element of a list is O(n). Sorting the list is O(nlogn). – Kenster May 26 '14 at 12:38
And converting array to list? – Deepu--Java May 26 '14 at 12:39
FYI I am using array not list. – Deepu--Java May 26 '14 at 12:40

chresse · Answer 3 · 2014-05-26T12:55:19.110

This can be done by reflection. The following code converts each property of the class into an double and compares it to the others.

public class MyClass {
    double value1;
    double value2;
    double value3;

    double getMax() throws IllegalArgumentException, IllegalAccessException {
        double max = Double.MIN_VALUE;

        for (Field field : this.getClass().getDeclaredFields()) {
            if(max < (double)field.get(this)) {
                max = (double)field.getDouble(this);
            }
        }

        return max;
    }
}

NOTE: You have to ensure that each property can be casted into a double value.

score 0 · Answer 4 · answered May 26 '14 at 13:09

If the maxValue method is called very frequently I would suggest to build your logic in the setter ie define all fields as private/protected and then also define a variable maxValue. Your setter logic would look something like this.

setValue1(double value1){
    if( getValue1() == maxValue() && value1 < maxValue()){
    //.. Check each of value1 .. 20 for the max Value and Assign if
    }else if(value1 > maxValue()){
    maxValue = value1;
    }
}

This would be more efficient even if you are using an array, as you need to scan the entire array/fields only when the value you are setting is less than the current max value and the maxValue is same as the current value (another optimization when using the array would be to store the index of the maxValue and then scan the entire array only when you are reducing the field value and it is the current maxValue field.

Find the max value in local parameters

4 Answers4