CODEWITHSUNDEEP
javaarraylist
user2665140
user2665140

Reputation: 136

Get an item within an arraylist of an arraylist

import java.util.ArrayList;

public class ArrayListPractice {
   public static void main(String[] args){
        ArrayList arr = new ArrayList();
        arr.add(10);
        arr.add(20);
        // arr is now [10,20]
        ArrayList arr2 = new ArrayList();
        arr2.add(new ArrayList(arr));
        arr2.add(30);
        // arr2 is now [[10,20],30]
        System.out.println(arr2.get(0)); // Prints out [10,20]
   }
}

I can print out the first element of arr2. But how can I print out the first element of the first element? (I want to print out 10 from arr2.)

Upvotes: 0

Views: 68

Answers (1)

Tim
Tim

Reputation: 4274

You need to cast arr2.get(0) to ArrayList so you can call the get method on it (your ArrayList ArrayList arr = new ArrayList(); is not typed - so it holds instances of Object).

Like this:

package test;
import java.util.ArrayList;

public class ArrayListPractice {
   public static void main(String[] args){
        ArrayList arr = new ArrayList();
        arr.add(10);
        arr.add(20);
        // arr is now [10,20]
        ArrayList arr2 = new ArrayList();
        arr2.add(new ArrayList(arr));
        arr2.add(30);
        // arr2 is now [[10,20],30]
        System.out.println(((ArrayList)arr2.get(0)).get(0)); // Prints out [10]
   }
}

Upvotes: 1

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