Vector in Java | Java Vector Class with Examples
By Rohan Vats
Updated on Nov 23, 2022 | 9 min read | 7.7k views
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By Rohan Vats
Updated on Nov 23, 2022 | 9 min read | 7.7k views
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Table of Contents
In programming, one of the most commonly used data structures is Vector in Java. Arrays are static data structures that can linearly store data. Similarly, vector in java also store the data linearly, but they are not restricted to a fixed size. Instead, its size can grow or shrink as per requirement. The parent class is AbstractList class and is implemented on List Interface.
Before you start to use vectors, import it from the java.util.package as follow:
import java.util.Vector
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Here is how a vector in java is declared:
public class Vector<V> extends AbstractList<V>
implements List<V>, RandomAccess, Cloneable, Serializable
Here, V is the type of element which can be int, string, char, etc.
Like we access data members in arrays, we can do that in vectors, too, by using the element’s index. For example, the second element of Vector E can be accessed as E[2].
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Some common errors made while declaring a vector in java:
1. Vector(int initialCapacity, int Increment)
This creates a vector in java with an initial capacity as specified, and the increment is also specified. With increment, the number of elements allocated each time the vector is resized upward is specified.
Syntax: Vector<V> e = new Vector<V>(int initialCapacity, int Increment);
2. Vector(int initialCapacity)
It creates a vector in java with an initial capacity equal to size as specified.
Syntax: Vector<V> e = new Vector<V>(int initialCapacity);
3. Vector()
It creates a vector in java with an initial default capacity of 10.
Syntax: Vector<V> e = new Vector<V>();
4. Vector(Collection c)
It creates a vector in java whose elements are those of collection c.
Syntax: Vector<V> e = new Vector<V>(Collection c);
Here is an example to demonstrate the creation and use of a vector in java:
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Code
import java.util.*;
public class Main{
public static void main(String[] args)
{
// Create default vector
Vector a = new Vector();
// Create a vector of specified Size
Vector b = new Vector(20);
// Create a vector of specified Size and Increment
Vector c = new Vector(30,10);
b.add(100);
b.add(200);
b.add(300);
// Create a vector with a specified collection
Vector d = new Vector(b)
System.out.println(“Vector a of capacity ” + a.capacity());
System.out.println(“Vector b of capacity ” + b.capacity());
System.out.println(“Vector c of capacity ” + c.capacity());
System.out.println(“Vector d of capacity ” + d.capacity());
}}
Output
Note: .capacity() is used to return the capacity of the vector.
A vector in java has three protected parameters as follows:
1. Int elementCount()- It tells the number of elements a vector contains
2. Int capcityIncremen()- When the vector’s size becomes greater than the capacity, the capacity is automatically increased with this.
3. Object[] elementData()- Elements of the vector are stored in array.
Here are some frequently used methods of vector in java:
Boolean add(Object o)- An element is appended at the end of the vector
Void add( int index V element)- The given element is added to the specified index in the vector
Code for adding the elements in Vector in java:
import java.util.*;
import java.io.*;
public class AddElementsToVector {
public static void main(String[] arg)
{
// Create a default vector
Vector a = new Vector();
// Adding elements using add() method
a.add(1);
a.add(2);
a.add(“vect”);
a.add(“for”);
a.add(3);
System.out.println(“Vector a is ” + a);
// Create a generic vector
Vector<Integer> b = new Vector<Integer>();
b.add(0);
b.add(1);
b.add(2);
System.out.println(“Vector b is ” + b);
}
}
Output
Boolean Remove(object o) – used to remove the element at the specified index in the vector
When the element is removed, all the elements are shifted left to fill the spaces; the indices are then updated.
Code to illustrate the removal of elements from vector in java:
import java.util.*;
import java.io.*;
public class Remove {
public static void main(String[] arg)
{
// Create a default vector
Vector a = new Vector();
// Adding elements using add() method
a.add(1);
a.add(2);
a.add(“vect”);
a.add(“for”);
a.add(4);
// Remove element
a.remove(2);
// Check
System.out.println(“after removal: ” + a);
}
}
Output
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The set () method can be used to change the element after adding the elements. The element’s index can be referenced as a vector is indexed. This method takes the index and the updated element.
Code to change the elements in vector in java
import java.util.*;
public class Update {
public static void main(String args[])
{
// Create an empty Vector
Vector<Integer> a = new Vector<Integer>();
// Add elements
a.add(1);
a.add(2);
a.add(3);
a.add(10);
a.add(20);
// Display
System.out.println(“Vector: ” + a);
// Replace
System.out.println(“Replacing”
+ a.set(0, 22));
System.out.println(“Replacing “
+ a.set(4, 50));
// Display the modified vector
System.out.println(“The new Vector is:” + a);
}
}
Output
There are several ways to loop through a vector. One of them is the get() method. Here is a program to iterate the elements in a Vector in java:
import java.util.*;
public class Iterate {
public static void main(String args[])
{
// creating an instance of vector
Vector<String> a = new Vector<>();
// Add elements using add() method
a.add(“vector”);
a.add(“in”);
a.add(1, “java”);
// Use Get method and the for loop
for (int i = 0; i < a.size(); i++) {
System.out.print(a.get(i) + ” “);
}
System.out.println();
// Use for each loop
for (String str : a)
System.out.print(str + ” “);
}
}
Output
Read: Java Architecture & Components
As seen above, vectors do not have a defined size. Instead, a vector in java can change its size dynamically. It is assumed that the vectors allocate indefinite space to store elements. However, it is not so. The vector’s size is changed based on two fields- ‘capacity increment ‘ and ‘capacity.’
When a vector is declared, a ‘capacity’ field equal to the size is allocated, and elements equal to the capacity can be added. As soon as the next element is inserted, the array’s size is increased by ‘capacityIncrement’ size. This gives the vector ability to change its size—the capacity doubles for a default constructor when a new element is inserted.
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The dynamic size of vectors avoids memory wastage, and the size of our data structure can be changed any time in the middle of the program.
Both vectors and ArrayLists are dynamic. However, vectors are more advantageous as:
A vector in java is a dynamic array with no size limit that is part of the Java Collection Framework since Java 1.2. We saw various constructors and popularly used methods of vectors in this blog. It is also worth attention that the Vector class should be used in a thread-safe environment only.
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