Java Vector ensureCapacity() Method

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Description

The ensureCapacity(int minCapacity) method is used to increases the capacity of this vector, if necessary.This is to ensure that the vector can hold at least the number of components specified by the minimum capacity argument.If the current capacity of this vector is less than minCapacity, then its capacity is increased by replacing its internal data array, kept in the field elementData, with a larger one. The size of the new data array will be the old size plus capacityIncrement.If the value of capacityIncrement is less than or equal to zero then the new capacity will be twice the old capacity.But if this new size is still smaller than minCapacity, then the new capacity will be minCapacity.

Declaration

Following is the declaration for java.util.Vector.ensureCapacity() method

public void ensureCapacity(int minCapacity)

Parameters

minCapacity − This is the desired minimum capacity.

Return Value

It returns void.

Exception

NA

Ensuring capacity of Vector of Integers Example

The following example shows the usage of Java Vector ensureCapacity(E) method to add Integers. We're adding couple of Integers to the Vector object using add() method calls per element and using ensureCapacity(), we're increasing its capacity to hold more items then print each element to show the elements added.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {
      
      // create an empty vector 
      Vector<Integer> vector = new Vector<>();

      // use add() method to add elements in the vector
      vector.add(20);
      vector.add(30);
      vector.add(20);
      vector.add(30);
      vector.add(15);
      vector.add(22);
      vector.add(11);
	  
      // this will increase the capacity of the Vector to 15 elements
      vector.ensureCapacity(15);

      // let us print all the elements available in vector
      System.out.println("Vector = " + vector);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Vector = [20, 30, 20, 30, 15, 22, 11]

Ensuring capacity of Vector of Strings Example

The following example shows the usage of Java Vector ensureCapacity(E) method to add Strings. We're adding couple of Strings to the Vector object using add() method calls per element and using ensureCapacity(), we're increasing its capacity to hold more items then print each element to show the elements added.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {
      
      // create an empty vector
      Vector<String> vector = new Vector<>();

      // use add() method to add elements in the vector
      vector.add("Welcome");
      vector.add("To");
      vector.add("Tutorialspoint");
	  
      // this will increase the capacity of the Vector to 15 elements
      vector.ensureCapacity(15);

      System.out.println("Vector = " + vector);      
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Vector = [Welcome, To, Tutorialspoint]

Ensuring capacity of Vector of Objects Example

The following example shows the usage of Java Vector ensureCapacity(E) method to add Student objects. We're adding couple of Student objects to the Vector object using add() method calls per element and using ensureCapacity(), we're increasing its capacity to hold more items then print each element to show the elements added.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty vector
      Vector<Student> vector = new Vector<>();

      // use add() method to add elements in the vector
      vector.add(new Student(1, "Julie"));
      vector.add(new Student(2, "Robert"));
      vector.add(new Student(3, "Adam"));


      // this will increase the capacity of the Vector to 15 elements
      vector.ensureCapacity(15);
	  
      System.out.println("Vector = " + vector);      
   }
}

class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Vector = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]