09 Jul Vectors in Java

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.

Create and Declare Vectors

We can declare a vector using any of the following two ways:

1. Vector<String> v = new Vector<String>(); ✅ Recommended

• Generics are used here.
• This means the Vector will only store String objects. We can create for other types as well.
• Type safety is enforced at compile time. For example, if you try to add an Integer, the compiler will throw an error.

2. Vector v = new Vector(); ❎ Discouraged

• Raw type (no generics).
• This means the Vector can store objects of any type (Strings, Integers, custom objects, etc.).
• Type safety is not enforced at compile time. You could accidentally mix types.

The following are the methods provided by Vectors,

Methods

Let us learn about the methods in Vectors,

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

Example – Create a Vector and perform operations

// Create a Vector

import java.util.Vector;

class Demo70 {
    static void main(String[] args) {

        Vector v = new Vector();
        System.out.println(v.size());

        Vector subjects = new Vector(10);
        System.out.println(subjects.size());

        subjects.addElement("PHP");
        subjects.addElement("Maths");
        subjects.addElement("Java");
        subjects.addElement("English");
        subjects.addElement("Science");
        subjects.addElement("IT");
        subjects.addElement("DS");
        subjects.addElement("Algorithms");
        subjects.addElement("Physics");
        subjects.addElement("AI");
        subjects.addElement("TOC");

        // Displaying in a line
        System.out.println(subjects);

        System.out.println(subjects.size());

        for (int i = 0; i < subjects.size(); i++) {
            System.out.println("Elements at index "+i+" = "+subjects.elementAt(i));
        }

        // Fetching a specific element using an index
        System.out.println(subjects.elementAt(5));

        // Insert an element at a specific index
        subjects.insertElementAt("GenAI", 2);

        System.out.println("Updated Vector...");
        for (int i = 0; i < subjects.size(); i++) {
            System.out.println("Elements at index "+i+" = "+subjects.elementAt(i));
        }

        System.out.println(subjects.size());

        // Find a specific element
        System.out.println("Does your vector has subject Algorithms? = "+subjects.contains("Algorithms"));

        // Removing elements
        subjects.removeElementAt(2);
        subjects.removeElementAt(5);
        subjects.removeElementAt(7);
        subjects.removeElementAt(8);

        System.out.println("Updated Vector...");
        for (int i = 0; i < subjects.size(); i++) {
            System.out.println("Elements at index "+i+" = "+subjects.elementAt(i));
        }

        System.out.println(subjects.size());
    }
}

The following is the output,

0
0
[PHP, Maths, Java, English, Science, IT, DS, Algorithms, Physics, AI, TOC]
11
Elements at index 0 = PHP
Elements at index 1 = Maths
Elements at index 2 = Java
Elements at index 3 = English
Elements at index 4 = Science
Elements at index 5 = IT
Elements at index 6 = DS
Elements at index 7 = Algorithms
Elements at index 8 = Physics
Elements at index 9 = AI
Elements at index 10 = TOC
IT
Updated Vector...
Elements at index 0 = PHP
Elements at index 1 = Maths
Elements at index 2 = GenAI
Elements at index 3 = Java
Elements at index 4 = English
Elements at index 5 = Science
Elements at index 6 = IT
Elements at index 7 = DS
Elements at index 8 = Algorithms
Elements at index 9 = Physics
Elements at index 10 = AI
Elements at index 11 = TOC
12
Does your vector has subject Algorithms? = true
Updated Vector...
Elements at index 0 = PHP
Elements at index 1 = Maths
Elements at index 2 = Java
Elements at index 3 = English
Elements at index 4 = Science
Elements at index 5 = DS
Elements at index 6 = Algorithms
Elements at index 7 = AI
8

In this lesson, we learned about Vectors and the usage of its methods.