Vector Class and its methods
Before we start with Vector let us look at the following concepts
1. Legacy Classes
2. Collection Hierarchy
Legacy Classes
Legacy classes are those classes with the help of which we store various datas or Objects. These were present in JDK 1.0 version. The various legacy classes are Vector, Stack, HashTable,Properties,Dictionary.
Collection Hierarchy
The below diagram shows the Collection hierarchy consisting of classes and interfaces.
As per the scope of the blog our discussion will be limited to the Vector class
What is Vector class ?
Vector class is an implemented class of List interface,Collection interface and Iterable interface which is used to store multiple elements. Vector class is a legacy class which was introduced in JDK 1.0. It comes from “java.utils” package. Vector class is an index based data structure and its underline data structure is growable or resizeable array. Duplicate elements can be stored in Vector class. Vector class allows any number of null values to be stored in it. Vector class follow the order of insertion. Vector class elements can be iterated by using Iterator and ListIterator methods as well as by Enumeration. Vector class is both thread safe and synchronized. It is slower due to synchronization. Its initial capacity is 10 and its threshold is when the current capacity is exceeded. Vector can double its size.
Methods of Vector class
Below are some of the methods of Vector class:
| Method Name | Description |
| add(Object e) | This method is used to add a new element of any datatype into the Vector class. |
| addAll(Collection c) | This method is used to add all elements of different datatypes into the Vector class. |
| clear() | It is used to clear all the elements from the Set interface but it does not clear the Vector class. |
| contains(Object o) | This method is used to check the presence of a Collection element in the Vector class. It returns ‘true’ value if the element is present in Vector class and ‘false’ value if the element is not present in the Vector class. |
| containsAll(Collection c) | This method is used to check if the Vector class contains all the collection elements. It returns ‘true’ value if all the elements are present in Vector class and ‘false’ value if any one of the element is not present in the Vector class. |
| isEmpty() | This method checks if the given Vector class is empty |
| iterator() | This method is used to iterate sequentially all the Collection elements present in a Vector class. |
| remove(Object o) | This method is used to remove a specified collection element from the Vector class. |
| removeAll(Collection c) | This method removes all those Collection elements from the current Vector class which are present in another Vector class. |
| retainAll(Collection c) | This method retains all those elements from the current Vector class which are present in another Vector class and removes those elements which are present in current Vector class but not in another Vector class and vice versa. |
| size() | This method is used to find out and display the number of Collection elements present in the Vector class. |
| toArray() | This method is used to convert all collection elements present in Vector class into an array. |
| toString() | This method is used to convert all collection elements present in Vector class into a String. |
| equals() | This method is used to check if two Vector classes are equal. It returns ‘true’ value if elements as well as size of elements present in one Vector class is equal to the elements and its size present in another Vector class. If the elements and the size of elements present in one Vector class is not equal to the elements and its size present in another Vector class then it returns ‘false’ value. |
| clone() | This method is used to create a shallow copy of the elements present in the Vector class. |
| addElement(Object obj) | It is used to add an element at the end of the Vector |
| firstElement() | It is used to display the first element of the Vector class. |
| lastElement() | It is used to display the last element of the Vector class. |
| removeElement(Object obj) | It is used to remove a particular element from Vector class. |
| removeAllElements() | It is used to remove all the elements from Vector class. |
| removeElementAt(int index) | It is used to remove a Vector element present at a particular index position. |
| get(int index) | It is used to display an element of Vector class present at a particular index. |
| set(int index,Object element) | It is used to replace a Vector class element present at a particular index position with another element. |
| capacity() | It is used to display the current capacity of the Vector or length of the array present in the Vector class. |
| elements() | It is used to display the enumeration of elements present in the Vector class. |
| listIterator() | This method is used to iterate sequentially in forward as well as backward direction all the Collection elements present in the Vector class. |
| indexOf(Object o) | It is used to display the index of first occurrence of Vector class element.It gives-1 if the specified element is not present in Vector class. |
1.Let us check the usage of add(Object e) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println(a1);
}
}
Output: [hello, c, 3.4, true, null, 3.55, Hiii]
Screenshot:
2. Let us check the usage of addAll(Collection c) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
a2.addAll(a1);
System.out.println(a2);
}
}
Output: [Hi, Hey, 16, 20, 23, 34]
Screenshot:
3. Let us check the usage of clear() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
a1.clear();
System.out.println(a1);
}
}
Output: []
Screenshot:
4. Let us check the usage of contains(Object o) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("The given Vector class contains: "+a1.contains(16));
System.out.println("The given Vector class contains: "+a1.contains("Harish"));
}
}
Output: The given Vector class contains: true
The given Vector class contains: false
Screenshot:
5. Let us check the usage of containsAll(Collection c) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
a2.add("Hi");
a2.add("Hey");
a2.add(16);
a2.add(20);
System.out.println("Does a2 contains all elements of a1:"+a2.containsAll(a1));
System.out.println("Does a1 contains all elements of a2:"+a1.containsAll(a2));
}
}
Output:
Does a2 contains all elements of a1:false
Does a1 contains all elements of a2:true
Screenshot:
6. Let us check the usage of isEmpty() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
System.out.println("Is a1 Vector class empty?: "+a1.isEmpty());
System.out.println("Is a2 Vector class empty?: "+a2.isEmpty());
}
}
Output:
Is a1 Vector class empty?: false
Is a2 Vector class empty?: true
Screenshot:
7. Let us check the usage of iterator() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Iterator;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Iterator a2= a1.iterator();
System.out.println("The collection elements values are: ");
while(a2.hasNext())
{
System.out.println(a2.next());
}
}
}
Output:
The collection elements values are:
hello
c
3.4
true
null
3.55
Hiii
Screenshot:
8. Let us check the usage of remove(Object o) method in Vector class.
Case 1: For removing an element containing words:
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
a1.remove("Hey");
a1.remove("Hi");
System.out.println(a1);
}
}
Output: [16, 20, 23, 34]
Screenshot:
Case 2: For removing an element containing numeric value:
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
a1.remove(2);
System.out.println("The elements present in Vector class after removing 16 from 2nd index:"+a1);
a1.remove(4);
System.out.println("The 4th index is chosen from the list of elements present after removing 16");
System.out.println("The elements present in Vector class after removing 34 from 4th index:"+a1);
}
}
Output: The elements present in Vector class after removing 16 from 2nd index:[Hi, Hey, 20, 23, 34]
The 4th index is chosen from the list of elements present after removing 16
The elements present in Vector class after removing 34 from 4th index:[Hi, Hey, 20, 23]
Screenshot:
9. Let us check the usage of removeAll(Collection c) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
a2.add("Hi");
a2.add("Hey");
a2.add(16);
a2.add(20);
a1.removeAll(a2);
System.out.println("Elements present in a1 after removing a2 elements from a1 are:"+a1);
}
}
Output:
Elements present in a1 after removing a2 elements from a1 are:[23, 34]
Screenshot:
10. Let us check the usage of retainAll(Collection c) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
a2.add("Hi");
a2.add("Hey");
a2.add(16);
a2.add(20);
a1.retainAll(a2);
System.out.println("Elements present in a1 after retaining a2 elements are:"+a1);
}
}
Output: Elements present in a1 after retaining a2 elements are:[Hi, Hey, 16, 20]
Screenshot:
11. Let us check the usage of size() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("The size of the collection elements present in the Vector class is: "+a1.size());
}
}
Output: The size of the collection elements present in the Vector class is: 6
Screenshot:
12. Let us check the usage of toArray() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Object a2[]= a1.toArray();
System.out.println("The list of array elements are:");
for(int i=0;i<=a2.length-1;i++)
{
System.out.println(a2[i]);
}
}
}
Output: The list of array elements are:
Hi
Hey
16
20
23
34
Screenshot:
13. Let us check the usage of toString() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println(a1.toString());
}
}
Output: [Hi, Hey, 16, 20, 23, 34]
Screenshot:
14. Let us check the usage of equals() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Vector a2= new Vector();
a2.add("Hi");
a2.add("Hey");
a2.add(16);
a2.add(20);
a2.add(23);
a2.add(34);
Vector a3= new Vector();
a3.add("Hi");
a3.add("Hey");
a3.add(16);
a3.add(20);
System.out.println("Is Vector class a1 equal to a2 ?:"+ a1.equals(a2));
System.out.println("Is Vector class a2 equal to a3 ?:"+ a2.equals(a3));
}
}
Output: Is Vector class a1 equal to a2 ?:true
Is Vector class a2 equal to a3 ?:false
Screenshot:
15. Let us check the usage of clone() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements in Vector class: "+a1);
Vector clonea1= new Vector();
clonea1=(Vector)a1.clone();
System.out.println("List of elements after using clone method:"+ clonea1);
}
}
Output: List of elements in Vector class: [Hi, Hey, 16, 20, 23, 34]
List of elements after using clone method:[Hi, Hey, 16, 20, 23, 34]
Screenshot:
16. Let us check the usage of addElement(Object obj) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
a1.addElement(343);
System.out.println(a1);
}
}
Output: [Hi, Hey, 16, 20, 23, 34, 343]
Screenshot:
17. Let us check the usage of firstElement() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements of Vector class are: "+a1);
System.out.println("The first element of Vector class is: "+a1.firstElement());
}
}
Output: List of elements of Vector class are: [Hi, Hey, 16, 20, 23, 34]
The first element of Vector class is: Hi
Screenshot:
18. Let us check the usage of lastElement() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements of Vector class are: "+a1);
System.out.println("The last element of Vector class is: "+a1.lastElement());
}
}
Output: List of elements of Vector class are: [Hi, Hey, 16, 20, 23, 34]
The last element of Vector class is: 34
Screenshot:
19. Let us check the usage of removeElement(Object obj) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements of Vector class are: "+a1);
a1.removeElement(16);
System.out.println("Elements present after removing 16 are :" +a1);
}
}
Output: List of elements of Vector class are: [Hi, Hey, 16, 20, 23, 34]
Elements present after removing 16 are :[Hi, Hey, 20, 23, 34]
Screenshot:
20. Let us check the usage of removeAllElements() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements of Vector class are: "+a1);
a1.removeAllElements();
System.out.println("No Element is present after removing all elements from Vector class :" +a1);
}
}
Output: List of elements of Vector class are: [Hi, Hey, 16, 20, 23, 34]
No Element is present after removing all elements from Vector class :[]
Screenshot:
21. Let us check the usage of removelElementAt(int index) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements of Vector class are: "+a1);
a1.removeElementAt(3);
System.out.println("Elements present after removing element present at index 3 are:" +a1);
}
}
Output: List of elements of Vector class are: [Hi, Hey, 16, 20, 23, 34]
Elements present after removing element present at index 3 are:[Hi, Hey, 16, 23, 34]
Screenshot:
22. Let us check the usage of get(int index) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements in Vector class are: "+a1);
System.out.println("The element present in index position 2 is: "+a1.get(2));
}
}
Output: List of elements in Vector class are: [Hi, Hey, 16, 20, 23, 34]
The element present in index position 2 is: 16
Screenshot:
23. Let us check the usage of set(int index,Object element) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("List of elements in Vector class are: "+a1);
System.out.println("The element to be replaced is: "+a1.set(2,56));
System.out.println("New List of elements after replacement are :" +a1);
}
}
Output: List of elements in Vector class are: [Hi, Hey, 16, 20, 23, 34]
The element to be replaced is: 16
New List of elements after replacement are :[Hi, Hey, 56, 20, 23, 34]
Screenshot:
24. Let us check the usage of capacity() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("The current capacity of this Vector class is: "+ a1.capacity());
}
}
Output: The current capacity of this Vector class is: 10
Screenshot:
25. Let us check the usage of elements() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
Enumeration e= a1.elements();
while(e.hasMoreElements())
{
System.out.println(e.nextElement());
}
}
}
Output: Hi
Hey
16
20
23
34
Screenshot:
26. Let us check the usage of listIterator() method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
ListIterator a2= a1.listIterator();
while(a2.hasNext()==true)
{
System.out.println("Next method "+a2.next());
}
while(a2.hasPrevious()==true)
{
System.out.println("Previous Method "+a2.previous());
}
}
}
Output: Next method Hi
Next method Hey
Next method 16
Next method 20
Next method 23
Next method 34
Previous Method 34
Previous Method 23
Previous Method 20
Previous Method 16
Previous Method Hey
Previous Method Hi
Screenshot:
27. Let us check the usage of indexOf(Object o) method in Vector class.
Code Snippet:
package vectorClass;
import java.util.Vector;
public class VectorClass {
public static void main(String[] args) {
Vector a1= new Vector();
a1.add("Hi");
a1.add("Hey");
a1.add(16);
a1.add(20);
a1.add(23);
a1.add(34);
System.out.println("Index of 16 is :"+a1.indexOf(16));
System.out.println("Index of 45 is :"+a1.indexOf(45));
}
}
Output: Index of 16 is :2
Index of 45 is :-1
Screenshot:
Difference between ArrayList and Vector
| SL NO: | ArrayList | Vector |
| 1 | It is not a Legacy class | It is a Legacy class |
| 2 | Neither thread safe nor synchronized | Both thread safe and synchronized |
| 3 | Faster due to no synchronization | Slower due to synchronization |
| 4 | Size increases by 50% | Size gets doubled. |
| 5 | Belongs to Collection framework | Belongs to original version of Java(1.0) |
| 6 | Iterator,ListIterator are used. | Enumeration,Iterator and ListIterator are used. |
Conclusion
Vector class is used for handling all the Collection elements in an effective way. It is necessary to understand the usage of all the methods of Vector class for better handling of Collection elements. Remember to practise, stay updated with the latest trends in Automation Software Testing Course,and maintain a positive attitude throughout your interview process. By thoroughly understanding the Vector class and its methods developers and testers can utitlise those concepts in their real life tasks.
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