Java ArrayList trimToSize() Method

June 7, 2023

What is ArrayList in Java ?

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

Java ArrayList trimToSize() Method :

The Java ArrayList class’s trimToSize() method reduces an instance’s capacity to match the list’s current size. Using this method, you can reduce the size of an ArrayList instance to the number of elements it has.

Syntax :

public void trimToSize()

Parameters : It does not take any parameter . we can simply use trimToSize() Method by using dot operator like list.trimToSize()

Throws Exception : It does throws any exceptions and error.

Return Value : It provides no value in return. It reduces this ArrayList instance's capacity to the number of the elements it has.

Polymorphism in Java

Encapsulation in Java

Abstraction in Java

Multithreading in Java

Example 1 :

Run

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

        //ArrayList object creation of size 8.
        ArrayList<String> list = new ArrayList<>(8);

        //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);
        
        //Trimming the list to size
        list.trimToSize();

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

Output :

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

Explanation : In the example above, we initially created an Array of size 8 and added only 6 values to it, leaving two extra spaces. We therefore used the trimToSize() method to remove the extra spaces in order to minimize this problem.
By this way we optimize the code with respect to space Complexity.

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