How to get minimum and maximum value from List of Objects using Java 8

Question

I have class like:

public class Test {
    private String Fname;
    private String Lname;
    private String Age;
    // getters, setters, constructor, toString, equals, hashCode, and so on
}

and a list like List<Test> testList filled with Test elements.

How can I get minimum and maximum value of age using Java 8?

I hate to sound like a broken record, but... What have you tried? Show us some code and a specific error or problem. — Jashaszun
– Jashaszun, Commented Jun 26, 2015 at 23:09
Since you specified, that you want to use Java 8, take a look at Streams. You should be able to figure out the rest on your own. — Turing85
– Turing85, Commented Jun 26, 2015 at 23:10

Pshemo · Accepted Answer · 2016-01-05 22:21:45Z

26

To simplify things you should probably make your age Integer or int instead of Sting, but since your question is about String age this answer will be based on String type.

Assuming that String age holds String representing value in integer range you could simply map it to IntStream and use its IntSummaryStatistics like

IntSummaryStatistics summaryStatistics = testList.stream()
        .map(Test::getAge)
        .mapToInt(Integer::parseInt)
        .summaryStatistics();

int max = summaryStatistics.getMax();
int min = summaryStatistics.getMin();

edited Jan 5, 2016 at 22:21

answered Jun 26, 2015 at 23:30

Pshemo

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4 Comments

Brian Goetz Over a year ago

No need for the double-map; just mapToInt(Test::getAge), the unboxing will be done for you.

Pshemo Over a year ago

@BrianGoetz Not quite. Notice that getAge returns String not int.

Brian Goetz Over a year ago

Who writes domain objects that store numbers in strings? Sheesh. :)

Brian Goetz Over a year ago

OK, but returning to the domain of useful, the point I was trying to make was: lambda conversion will do necessary adaptation like widening, boxing, casting, etc, to make up differences between the natural type of the lambda and the target type -- that one need not manually insert adaptations like unboxing.

lasclocker · Accepted Answer · 2019-06-15 03:54:28Z

2

max age:

   testList.stream()
            .mapToInt(Test::getAge)
            .max();

min age:

   testList.stream()
            .mapToInt(Test::getAge)
            .min();

edited Jun 15, 2019 at 3:54

answered Jun 15, 2019 at 3:38

lasclocker

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