Java ArrayList concept

Question

How do you loop through an ArrayList within an ArrayList?

For example, If I have an ArrayList called plants of Plant objects. And each Plant object has a random number of flowerNames inside. How do I go through the ArrayList, stop at each Plant and print out the Plant's list of flowerNames? (just an example) and then move on to the next Plant, etc.

Plant: has an ArrayList of Flowers: has an ArrayList of flowerNames

Plant is in one class, Flowers is in another class

Is there a way to do this with the standard for loop? Not interate...?

Loops can be nested. Give it a try and write some code.

Matt Ball
– Matt Ball

2013-02-08 06:25:20 +00:00
Commented Feb 8, 2013 at 6:25 — Matt Ball
– Matt Ball, Commented Feb 8, 2013 at 6:25
Use Lambdaj or Guava for their awesomeness

Batakj
– Batakj

2013-02-08 07:30:12 +00:00
Commented Feb 8, 2013 at 7:30 — Batakj
– Batakj, Commented Feb 8, 2013 at 7:30

Petr Mensik · Accepted Answer · 2013-02-08 06:45:55Z

3

Try something like this .

for( Plant plant : plants) {
    for(Flowers flower : plant.getFlowers()) {
        System.out.println(flower.getName());
    } 
}

edited Feb 8, 2013 at 6:45

Petr Mensik

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answered Feb 8, 2013 at 6:26

vikiiii

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Comments

Achintya Jha · Accepted Answer · 2013-02-08 06:28:51Z

0

    ArrayList<Object> outerList = new ArrayList<Object>();
    ArrayList<Object> innerList = new ArrayList<Object>();

    for(Object outer: outerList){
        for(Object inner: innerList){

            //Perform operation with innerList. Print or something else.
        }
    }

answered Feb 8, 2013 at 6:28

Achintya Jha

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Comments

uday · Accepted Answer · 2013-02-08 06:50:41Z

0

if you are not sure at which position you will get another list object use instance of method and check. Sample code is here.

for(int i=0;i<l1.size();i++){
    if(!(l1.get(i) instanceof List<?>)){
    System.out.println(l1.get(i));
    }
    else {
    for(int j=0;j<((List)l1.get(i)).size();j++){
        System.out.println(((List)l1.get(i)).get(j));
    }
    }
    }

answered Feb 8, 2013 at 6:50

uday

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