Java ArrayList ensureCapacity() Method

December 13, 2022

What is ArrayList in Java ?

Arraylist is a part of collection framework in java. It contains several inbuilt function like ensureCapacity()method which can be found in the java.util.ArrayList Package. It implements the List interface of the collections framework.

Java ArrayList ensureCapacity() Method :

The ensureCapacity() function of the Java.util package. If necessary, the ArrayList class extends this ArrayList instance’s capacity to make sure it can carry at least the amount of elements indicated by the minimum capacity argument.

Syntax :

public void ensureCapacity(int minCapacity)

Parameters : minCapacity - the desired minimum capacity

Throws Exception : It does throws any exceptions and error.

Return Value : It provides no value in return.

clear() Function in ArrayList

clone() Function in ArrayList

add() Function in ArrayList

addall() Function in ArrayList

Example 1 :

Run

import java.util.*;
public class Main {
    public static void main(String[] args) {

        //ArrayList object creation
        ArrayList<String> list = new ArrayList<>();

        //Adding elements to the list
        list.add("A");
        list.add("B");
        list.add("C");
        list.add("D");
        list.add("E");
        list.add("F");

        
        //Printing the initial list.
        System.out.println("ArrayList : " + list);
        
        //Ensuring the minimum size of the list so it can hold at least 12 elements.
        list.ensureCapacity(12);

        //Printing the list after ensureCapacity()
        System.out.println("ArrayList after ensureCapacity() : " + list);
    }
}

Output :

ArrayList : [A, B, C, D, E, F]
ArrayList after trimToSize() : [A, B, C, D, E, F]

Explanation : In the preceding example, we initially created the ArrayList of undefined size, and we are unsure of the number of elements it can hold. To ensure this, we have used the ensureCapacity() method to hold at least the desired number of elements; in this case, we have passed the minimum value of 10 to ensure that until the 10th element it can easily store the value.

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