How to call methods on arrays within an ArrayList?

Question

I've created an ArrayList called groupOfPeople by having a constructor that takes their name and ages. This was added to the ArrayList like this:

groupOfPeople.add(new Person(23,"Tom"));

Now I want to make that person call a sleep() method that is stored within another class. I've called it like this:

SleepClass callSleepClassr = new SleepClass();

Now I want to call the first person in the ArrayList and make them sleep so adding .callSleepClass.sleep() to them. The thing is, I don't know how to refer to that first array.

Any help is appreciated, thank you.

for (Person x : people) { x.callshower.shower(); } doesn't work, how would I make x do this? — James
– James, Commented Dec 3, 2016 at 8:00

Aimee Borda · Accepted Answer · 2016-12-03 08:02:16Z

1

By using Java8 streams, you can include the check for empty list as well,

groupOfPeople.stream().findFirst().ifPresent(SleepClass::sleep);

The sleep method should take a Person parameter then.

answered Dec 3, 2016 at 8:02

Aimee Borda

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ΦXocę 웃 Пepeúpa ツ · Accepted Answer · 2016-12-03 09:21:13Z

0

If you want to put the first element in the list to sleep then get the element at index 0 in the list and invoke the method:

if(!groupOfPeople.isEmpty()){
    groupOfPeople.get(0).callSleepClass.sleep();
}

answered Dec 3, 2016 at 9:21

ΦXocę 웃 Пepeúpa ツ

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user1211 · Accepted Answer · 2016-12-03 18:05:03Z

0

You can call the function on each element on the list by doing:

for (Person  p : groupOfPeople) {
    p.callSleepClass.sleep();               
}

If you want to do it for the first element in the list, you can use:

if(groupOfPeople.size()>1)
    groupOfPeople.get(0).callSleepClass.sleep();

edited Dec 3, 2016 at 18:05

answered Dec 3, 2016 at 8:19

user1211

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1 Comment

ΦXocę 웃 Пepeúpa ツ Over a year ago

this is not correct, op defined groupOfPeople as an ArrayList, not an Array

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