Q:

how to create an array of arraylist in java

ArrayList<Integer> integerArray = new ArrayList<Integer>();
ArrayList<String> integerArray = new ArrayList<String>();
ArrayList<Double> integerArray = new ArrayList<Double>();
//... keep replacing what is inside the <> with the appropriate
//data type
5
new ArrayList<>(Arrays.asList(array));
5
// Java code to demonstrate the concept of  
// array of ArrayList 
  
import java.util.*; 
public class Arraylist { 
    public static void main(String[] args) 
    { 
        int n = 5; 
  
        // Here al is an array of arraylist having 
        // n number of rows.The number of columns on 
        // each row depends on the user. 
        // al[i].size() will give the size of the 
        // i'th row 
        ArrayList<Integer>[] al = new ArrayList[n]; 
  
        // initializing 
        for (int i = 0; i < n; i++) { 
            al[i] = new ArrayList<Integer>(); 
        } 
  
        // We can add any number of columns to each 
        // rows as per our wish 
        al[0].add(1); 
        al[0].add(2); 
        al[1].add(5); 
        al[2].add(10); 
        al[2].add(20); 
        al[2].add(30); 
        al[3].add(56); 
        al[4].add(34); 
        al[4].add(67); 
        al[4].add(89); 
        al[4].add(12); 
  
        for (int i = 0; i < n; i++) { 
            for (int j = 0; j < al[i].size(); j++) { 
                System.out.print(al[i].get(j) + " "); 
            } 
            System.out.println(); 
        } 
    } 
} 
2
import java.util.ArrayList;
//create ArrayList
ArrayList<String> arrayList = new ArrayList<String>();
2
new ArrayList<>(Arrays.asList(array))
1
ArrayList<Type> name = new ArrayList<Type>();
3
ArrayList<Integer> integerArray = new ArrayList<Integer>();
ArrayList<String> stringArray = new ArrayList<String>();
ArrayList<Double> doubleArray = new ArrayList<Double>();
//... keep replacing what is inside the <> with the appropriate
//data type
2
//Create the Arraylist variable: . Replace the T with the type of 
//data to be stored in the list.
ArrayList<T> exampleList = new ArrayList<>();
//You can now perform operations on this ArrayList
0

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