Vector In Java

The Vector class implements a growable array of objects. It is like the dynamic array which can grow or shrink its size. It is found in java.util package and implements List interface. It is similar to ArrayList but there are two main differences :

It is similar to ArrayList but with two main differences

• Vector is synchronized
• Vector contains many legacy methods that are not part of the collections framework.

Vector is very useful when the array size is not known in advance or array that changes size over liftetime of program

Vector extends AbstractList and implements List<E> interfaace. However, the size of a Vector can grow or shrink as needed to accommodate adding and removing items after the Vector has been created. For official documentation on Vector please refere here

Declaration

public class Vector<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

Constructors

There are 3 constructors defined for Vector

• Vector() : Creates a default vector with initial capacity 10
• Vector(int size): Creates a vector whose initial capacity is specified by size.
• Vector(int size, int incr): Creates a vector whose initial capacity is specified by size and increment is specified by incr. It specifies the number of elements to allocate each time that a vector is resized upward.
• Vector(Collection c): Creates a vector that contains the elements of collection c.

If increment is specified, Vector will expand according to it in each allocation cycle but if increment is not specified then vector’s capacity get doubled in each allocation cycle.

Methods of Vector

Here are some of the Vector methods

Adding and retrieving elements from Vector

Vector provides add(Object ob), add(int index, Object obj), addAll(Collection c) and addAll(int index, Collection c) to add elements.

import java.util.ArrayList;
import java.util.Vector
;
public class VectorExample {
	public static void main(String[] args) {
		// Create Default Vector
		Vector vector = new Vector();
		vector.add(1);
		vector.add(2);
		vector.add("geeks");
		System.out.println("Vector after add(Object) : " + vector);
		vector.add(2, "for");
		System.out.println("Vector after add(index, object) : " + vector);
		ArrayList al = new ArrayList();
		al.add("1");
		al.add("2");
		vector.addAll(al);
		System.out.println("Vector after addAll(Collection) : " + vector);
		vector.addAll(3, al);
		System.out.println("Vector after addAll(index, Collection) : " + vector);
        vector.insertElementAt("com", vector.size() - 1);
		System.out.println("Vector after insertElementAt(object, index) : " + vector);
		vector.get(0);
		System.out.println("Vector after get(index) : " + vector);
	}

}

Output :
Vector after add(Object) : [1, 2, geeks]
Vector after add(index, object) : [1, 2, for, geeks]
Vector after addAll(Collection) : [1, 2, for, geeks, 1, 2]
Vector after addAll(index, Collection) : [1, 2, for, 1, 2, geeks, 1, 2]
Vector after insertElementAt(object, index) : [1, 2, journal, 1, 2, techi, 1, com, 2]
Vector after get(index) : [1, 2, journal, 1, 2, techi, 1, com, 2]

Removinng Elements in Vector

Vector Class provides clear(), remove(index), remove(object), removeAll(Collection c), removeAllElements(), removeElement(Object obj), removeElementAtIndex(index) and removeIf(Predicate filter) to remove elements from Vector.

import java.util.Arrays;
import java.util.Vector;

public class VectorDelete {
	public static void main(String[] args) {
		Vector<String> vector = new Vector<String>(Arrays.asList("Sachin", "Dravid", "Ganguly", "Laxman", "Sehwag", "Kohli", "Rohit", "Zaheer", "Kapil", "Gavaskar"));
		vector.remove(1);
		System.out.println("Vector after remove(index) : " + vector);
		vector.remove("Ganguly");
		System.out.println("Vector after remove(object) : " + vector);
		vector.removeAll(Arrays.asList("Laxman", "Sehwag"));
		System.out.println("Vector after remove(Collection c) : " + vector);
		vector.removeElement("Kohli");
		System.out.println("Vector after removeElement(object) : " + vector);
		vector.removeElementAt(4);
		System.out.println("Vector after removeElement(index) : " + vector);
		vector.removeIf(v -> v.startsWith("Roh"));
		System.out.println("Vector after removeIf(Predicate p) : " + vector);
		vector.removeAllElements();
		System.out.println("Vector after removeAllElements() : " + vector);
		
	}
}

Output :
Vector after remove(index) : [Sachin, Ganguly, Laxman, Sehwag, Kohli, Rohit, Zaheer, Kapil, Gavaskar]
Vector after remove(object) : [Sachin, Laxman, Sehwag, Kohli, Rohit, Zaheer, Kapil, Gavaskar]
Vector after remove(Collection c) : [Sachin, Kohli, Rohit, Zaheer, Kapil, Gavaskar]
Vector after removeElement(object) : [Sachin, Rohit, Zaheer, Kapil, Gavaskar]
Vector after removeElement(index) : [Sachin, Rohit, Zaheer, Kapil]
Vector after removeIf(Predicate p) : [Sachin, Zaheer, Kapil]
Vector after removeAllElements() : []

Vector vs ArrayList in Java

Vector and ArrayList both implement List interface and use dynamically resizable arrays for internal data structure.

ArrayList<T> arrList = new ArrayList<T>();
Vector<T> vector = new Vector<T>(); 

Conclusion

Vector is like the dynamic array which can grow or shrink its size. Unlike array, we can store n-number of elements in it as there is no size limit. It is a part of Java Collection framework since Java 1.2. It is recommended to use the Vector class in the thread-safe implementation only.

Thanks, Note

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