ArrayList ensureCapacity() method in Java with Examples - GeeksforGeeks

26 Nov, 2018
The ensureCapacity() method of java.util.ArrayList class increases the capacity of this ArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.
Syntax:
public void ensureCapacity(int minCapacity)
Parameters: This method takes the desired minimum capacity as a parameter.
Below are the examples to illustrate the ensureCapacity() method.
Example 1:
// Java program to demonstrate// ensureCapacity() method for Integer value  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          try {              // Creating object of ArrayList<Integer>            ArrayList<Integer>                arrlist = new ArrayList<Integer>();              // adding element to arrlist            arrlist.add(10);            arrlist.add(20);            arrlist.add(30);            arrlist.add(40);              // Print the ArrayList            System.out.println("ArrayList: "                               + arrlist);              // ensure that the ArrayList            // can hold upto 5000 elements            // using ensureCapacity() method            arrlist.ensureCapacity(5000);              // Print            System.out.println("ArrayList can now"                               + " surely store upto"                               + " 5000 elements.");        }          catch (NullPointerException e) {            System.out.println("Exception thrown : " + e);        }    }}
ArrayList: [10, 20, 30, 40]
ArrayList can now surely store upto 5000 elements.

Example 2:
// Java program to demonstrate// ensureCapacity() method for String value  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          try {              // Creating object of ArrayList<Integer>            ArrayList<String>                arrlist = new ArrayList<String>();              // adding element to arrlist            arrlist.add("A");            arrlist.add("B");            arrlist.add("C");            arrlist.add("D");              // Print the ArrayList            System.out.println("ArrayList: "                               + arrlist);              // ensure that the ArrayList            // can hold upto 400 elements            // using ensureCapacity() method            arrlist.ensureCapacity(400);              // Print            System.out.println("ArrayList can now"                               + " surely store upto"                               + " 400 elements.");        }          catch (NullPointerException e) {            System.out.println("Exception thrown : " + e);        }    }}
ArrayList: [A, B, C, D]
ArrayList can now surely store upto 400 elements.

Java - util package
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