ArrayList of ArrayList in Java
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We have discussed that an array of ArrayList is not possible without warning. A better idea is to use ArrayList of ArrayList.
// Java code to demonstrate the concept of // array of ArrayList import java.util.*; public class Arraylist { public static void main(String[] args) { int n = 3; // Here aList is an ArrayList of ArrayLists ArrayList<ArrayList<Integer> > aList = new ArrayList<ArrayList<Integer> >(n); // Create n lists one by one and append to the // master list (ArrayList of ArrayList) ArrayList<Integer> a1 = new ArrayList<Integer>(); a1.add(1); a1.add(2); aList.add(a1); ArrayList<Integer> a2 = new ArrayList<Integer>(); a2.add(5); aList.add(a2); ArrayList<Integer> a3 = new ArrayList<Integer>(); a3.add(10); a3.add(20); a3.add(30); aList.add(a3); for (int i = 0; i < aList.size(); i++) { for (int j = 0; j < aList.get(i).size(); j++) { System.out.print(aList.get(i).get(j) + " "); } System.out.println(); } } } |
Output:
1 2 5 10 20 30
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