Get specific element with highest value in ArrayList

Question

I'm new to java and I'm having a problem with ArrayList. I want to get the highest value from Jozef and Klaus.

ArrayList looks like:

|  Name        | Age|
+--------------+----+
| Jozef Coin   | 55 |    
| Jozef Coin   | 56 |    
| Jozef Coin   | 57 |
| Klaus Neumer | 34 |
| Klaus Neumer | 31 |
| Klaus Neumer | 59 |

This is my code so far, it only returns the highest value in the arraylist.

Person b = persons.get(0)

for(Person p: persons){    
      if(p.getAge() >= b.getAge()){    
         b = p;    
           System.out.println(b.toString());    
      }    
}

I'm probably way over my head but I'd love to know if this is possible and if so there is an solution to this.

Could you please clarify your question? What does the `Person` class look like? — Maljam, Apr 03 '16 at 04:57
So instead of highest in the list you want highest for each person? — Sam Orozco, Apr 03 '16 at 05:00

score 3 · Accepted Answer · answered Apr 03 '16 at 05:03

3

You can use Comparable for your task

public class CompareAge implements Comparator<Person> {
    @Override
    public int compare(Person p1, Person p2) {
        return p1.getAge().compareTo(p2.getAge());
    }
}

Then use that CompareAge class like as follows

Collections.sort(myArrayList, new CompareAge());
myArrayList.get(arrayList.size() - 1); //Retrieve the last object

answered Apr 03 '16 at 05:03

Shree Krishna

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Thanks, this was a great solution to the problem. – Ilja Apr 03 '16 at 05:08

score 0 · Answer 2 · answered Apr 03 '16 at 05:02

It's hard to answer unless we know the methods in the Person class, however this would be the general way I would do it.

Person b = persons.get(0)
int jozefHighest = 0;
int klausHighest = 0;

for(Person p: persons){

      if(p.getName().startsWith("Jozef") {
        if(p.getAge() > jozefHighest)
            jozefHighest = p.getAge)_
      } else if (p.getName().startsWith("Klaus")) {
        if(p.getAge() > klausHighest)
            klausHighest = p.getAge()
      }

}

score 0 · Answer 3 · answered Apr 03 '16 at 05:07

0

Java 8 is Cool!

    int[] a = {1,2,3,4};
    OptionalInt maxValue = IntStream.of(a).max();
    System.out.println("Max Value: " + maxValue);

answered Apr 03 '16 at 05:07

Suparna

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score 0 · Answer 4 · answered Apr 03 '16 at 05:57

0

You can do this in a single step in Java 8:

Map<String, Integer> oldestMap = persons.stream()
    .collect(Collectors.groupingBy(Person::getName,
        Collectors.maxBy(Person::getAge).get());

You now have a map from name to maximum age.

answered Apr 03 '16 at 05:57

sprinter

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Get specific element with highest value in ArrayList

4 Answers4

Java 8 is Cool!