Vectors in Java - Studyopedia

09 Jul Vectors in Java

Posted at 14:22h in Java by Studyopedia Editorial Staff 0 Comments

Vectors are growable arrays that need to be initialized before it is used. Vector is a Java class and to use it, import the java.util package like this,

import java.util.*;

The size is to be mentioned in Java Arrays before being used, and once set, it cannot be changed, unlike Vectors. Therefore, Vectors implement a dynamic array.

The following are the methods provided by Vectors,

Methods

Let us learn about the methods in Vectors,

Method	Description

void addElement(Object elements)	Add an element to the vector.
void insertElementAt(Object element, int index)	Insert an element at a specified index.
boolean removeElement(Object element)	Remove the first occurrence of the element.
void removeElementAt(int index)	Remove an element from a given index.
void removeAllElements()	Remove all the elements. Empties the vector and the size is set to 0.
Object firstElement()	Returns the first element.
Object lastElement()	Returns the last element.
Object ElementAt(int index)	Returns the element at a specified index.
int indexOf(Object element)	Returns the index of the first occurrence of the element
int lastIndexOf(Object element)	Returns the index of the last occurrence of the element
boolean contains(Object a[])	Returns true if the vector has elements.
boolean isEmpty()	True is returned if the vector is empty.
Object clone()	Returns the clone of the vector.
int capacity()	Returns the capacity of the vector.
int size()	Returns the count of elements in the vector
void trimToSize()	Sets capacity to the elements it currently holds
void setsize(int s)	Set a new size for the vector.

Now let us see an example to understand the working of Vectors in Java,

Example

import java.util.*;

public class StudyopediaDemo {

   public static void main(String args[]) {
	 
	 Vector vc = new Vector();
	 
	 System.out.println("\nLearning the usage of Vectors - Studyopedia ");
	 System.out.println("Elements (COUNT) in the Vector vc = "+vc.size());
	 
	 Vector subjects = new Vector (10);
	 System.out.println("Elements (COUNT) in the Vector subjects = "+subjects.size());
	 	 
	 subjects.addElement("PHP");	 
	 subjects.addElement("Maths");
	 subjects.addElement("Java");
	 subjects.addElement("English");
	 subjects.addElement("Science");
	 subjects.addElement("Fundamentals of IT");
	 subjects.addElement("Data Structures");
	 subjects.addElement("Algorithms");
	 subjects.addElement("Physics");
	 subjects.addElement("Artificial Inetlligence");
	 subjects.addElement("Theory of Computation");

         System.out.println("Elements (COUNT) in the Vector subjects = "+subjects.size());
	 
	 System.out.println("");
	 
	 for(int i=0; i<subjects.size();i++)
	   System.out.println("Element at index "+i+" = "+subjects.elementAt(i));

         // Inserting element at index 2
	 subjects.insertElementAt("Digital Electronics",2);
	 
	 System.out.println("");
	 System.out.println("After adding a new element in the Vector!");
	 for(int i=0; i<subjects.size();i++)
           System.out.println("Element at index "+i+" = "+subjects.elementAt(i));
	
	 // removing elements
	 subjects.removeElementAt(3);
	 subjects.removeElementAt(4);
	 subjects.removeElementAt(5);
	
         System.out.println("");
	 System.out.println("After removing three elements from the Vector!");	
	
	 System.out.println("");
	 for(int i=0; i<subjects.size();i++)
	   System.out.println("Element at index "+i+" = "+subjects.elementAt(i));

         // checking the size of the Vector now
         System.out.println("\nElements (COUNT) in the Vector subjects = "+subjects.size());

	 // finding the subject Maths
	 System.out.println("\nDoes your vector has subject Maths = "+subjects.contains("Maths")); 
  } 
}

The following is the output,

Vectors in Java