Vector in Java

Vector is a legacy class that works as a dynamic array. It was there in Java before collections framework was introduced in 1.2 version. Later, with introduction of collections framework, ArrayList took place of vector as far as non-multithreaded applications are concerned. But vector is still useful in multithreaded environments.

Important points about vector

1. Vector is a legacy class
2. It was made part of collections framework in java 1.2
3. Vector are dynamic arrays just like ArrayList
4. Vector are synchronized unlike ArrayList. Vector are thread-safe and can be used in a multithreaded application.
5. In non-multithreaded application, ArrayList would be a better choice.
6. Iterators returned by Vector are fail-fast. Which means if you change vector in structure, it will fail and throw ConcurrentModificationException

Class Declaration

public class Vector extends Object implements List, Cloneable, Serializable

Class Hierarchy

Constructors summary

Constructor	Description
Vector()	Constructs empty vector with initial capacity of 10.
Vector(int initialCapacity)	Constructs an empty vector with the specified initial capacity.
Vector(int initialCapacity, int capacityIncrement)	It constructs an empty vector with the specified initial capacity and capacityIncrement value.
Vector( Collection<? extends E> c)	Constructs a vector that contains the elements of a collection c.

Vector Example

package com.javatrainingschool;

import java.util.Vector;

public class VectorExample {

	public static void main(String[] args) {
		
		Vector<Integer> vector = new Vector<>();
		vector.addElement(10);
		//We can also use add method of Collection interface
        vector.add(20);
		vector.addElement(20);
		vector.addElement(30);
		vector.addElement(40);
		
		System.out.println("Size of the vector = " + vector.size());
		System.out.println("Index of number 30 = " + vector.indexOf(30));
		System.out.println("First element of the vector = " + vector.firstElement());
		System.out.println("Last element of the vector = " + vector.lastElement());
		
	}
	
}

Output :
Size of the vector = 5
Index of number 30 = 3
First element of the vector = 10
Last element of the vector = 40

Iterate Vector using Enumeration

package com.javatrainingschool;

import java.util.Enumeration;
import java.util.Vector;

public class VectorExample {

	public static void main(String[] args) {
		
		Vector<Integer> vector = new Vector<>();
		vector.addElement(10);
		//We can also use add method of Collection interface
                vector.add(20);
		vector.addElement(20);
		vector.addElement(30);
		vector.addElement(40);
		
		Enumeration<Integer> en = vector.elements();
		
		while(en.hasMoreElements()) {
			System.out.println("Element = " + en.nextElement());
		}
	}
}

Iterate Vector using enhanced for loop

package com.javatrainingschool;

import java.util.Vector;

public class VectorExample {

	public static void main(String[] args) {

		Vector<Integer> vector = new Vector<>();
		vector.addElement(10);
		// We can also use add method of Collection interface
		vector.add(20);
		vector.addElement(20);
		vector.addElement(30);
		vector.addElement(40);

		for (int number : vector) {
			System.out.println("Element = " + number);
		}
	}
}

Iterate vector using iterator

package com.javatrainingschool;

import java.util.Iterator;
import java.util.Vector;

public class VectorExample {

	public static void main(String[] args) {

		Vector<Integer> vector = new Vector<>();
		vector.addElement(10);
		// We can also use add method of Collection interface
		vector.add(20);
		vector.addElement(20);
		vector.addElement(30);
		vector.addElement(40);

		Iterator<Integer> it = vector.iterator();
		while(it.hasNext()) {
			System.out.println("Element = " + it.next());
		}
	}
}

Output :
Element = 10
Element = 20
Element = 20
Element = 30
Element = 40

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