CODEWITHSUNDEEP
javajava-8java-streamcomparator
Adam Amin
Adam Amin

Reputation: 1456

Find maximum and minimum double value in a list

I have the following list of double values:

items {9.0, 4.0, 16.0, -6.0, 5.0}

I want to find the maximum and minimum values and for that I did:

double max = items.stream().max(Comparator.comparing(String::valueOf)).get();
double min = items.stream().min(Comparator.comparing(String::valueOf)).get();

The result that I got is max=9.0 and min=-6.0. I was expecting the maximum to be 16.0. Later, I changed 16.0 to 92.0 and it worked; it gave me max=92.0

Do you know how to solve that?

Upvotes: 14

Views: 18124

Answers (6)

Paul Raj
Paul Raj

Reputation: 1

items .stream() .sorted() .limit(1) .collect(Colletors.toList();

Upvotes: -1

Youcef LAIDANI
Youcef LAIDANI

Reputation: 59950

What about :

double max = items.stream().mapToDouble(Double::doubleValue).max().getAsDouble();//16.0
double min = items.stream().mapToDouble(Double::doubleValue).min().getAsDouble();//-6.0

Upvotes: 12

ernest_k
ernest_k

Reputation: 45309

There's a more appropriate stream type for doubles. Using it, you can get min and max in one terminal operation (eliminating the need to supply a comparator in the process):

DoubleSummaryStatistics stats = items.stream().mapToDouble(d -> d)
 .summaryStatistics();
//even better: DoubleStream.of(9.0, 4.0, 16.0, -6.0, 5.0).summaryStatistics()

And stats will have:

count=5, sum=28.000000, min=-6.000000, average=5.600000, max=16.000000

Upvotes: 5

azro
azro

Reputation: 54148

Your are comparing them as String so by alphabetical order : 1xx is before 9xx

You need to compare then as Double or Integer, so use Comparator.comparing(Double::valueOf) (or Integer::valueOf)

Upvotes: 4

Thomas
Thomas

Reputation: 88707

You don't want to compare using strings but by the natural order of your double elements, i.e. Comparator.naturalOrder() instead of Comparator.comparing(String::valueOf).

Comparing via strings will result in the characters being compared and since the character value of 9 (of "9.0") is greater than 1 (of "16.0") you get the result you see. Changing "16.0" to "92.0" will result in . to be compared with 2 (since the first character is equal) and thus "92xx" is greater than "9.xx".

Upvotes: 12

Peter Lawrey
Peter Lawrey

Reputation: 533492

It appears you want to compare the number numerically instead of their String representation e.g. "16.0" < "9.0" as '1' < '9'

List<Double> items = Arrays.asList(9.0, 4.0, 16.0, -6.0, 5.0);
double max = items.stream().max(Comparator.naturalOrder()).get();
double min = items.stream().min(Comparator.naturalOrder()).get();
System.out.println(min + " " + max);

prints

-6.0 16.0

Upvotes: 7

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