Vector method addFirst() in Java

A Vector method addFirst() adds an element as the first element of this collection. Once an operation completed normally, a specified element appear as first position in this Vector.

Syntax

 1 default void addFirst(E e)

e : It is an element to be added at first position in this vector.

Exceptions:

1. NullPointerException : if the specified element is null and this collection does not permit null elements2. UnsupportedOperationException : if this collection implementation does not support this operation

Vector method addFirst()

 1 package iogyan.example;
 2 
 3 import java.util.Arrays;
 4 import java.util.Vector;
 5 
 6 public class Main {
 7 
 8     public static void main(String[] args) {
 9 
 10         Vector<Integer> vector = new Vector<>();
 11 
 12         // append elements into this vector
 13         vector.addAll(Arrays.asList(10, 20, 60, 30));
 14         System.out.println("A vector elements : " + vector);
 15 
 16         // add element at first position
 17         vector.addFirst(100);
 18         System.out.println("An updated vector elements :" + vector);
 19     }
 20 }

In the above example, a Vector of type Integer created and elements added using addAll() called by passing a collection. A addFirst() method called by passing a value that added as first position in this vector and print updated vector elements.

Output

 1 A vector elements : [10, 20, 60, 30]
 2 An updated vector elements :[100, 10, 20, 60, 30]

Vector method addFirst() with String

 1 package iogyan.example;
 2 
 3 import java.util.Arrays;
 4 import java.util.Vector;
 5 
 6 public class StringMain {
 7 
 8     public static void main(String[] args) {
 9 
 10         Vector<String> vector = new Vector<>(5);
 11 
 12         vector.addAll(Arrays.asList("Welcome", "to", "IOGyan"));
 13         System.out.println("A vector elements : " + vector);
 14 
 15         // add element at first position
 16         vector.addFirst("thanks");
 17         System.out.println("An updated vector elements :" + vector);
 18     }
 19 }

In the above example, a Vector of type String created and elements added using addAll() called by passing a collection. A addFirst() method called by passing a string that added as first position in this vector and print updated vector elements.

Output

 1 A vector elements : [Welcome, to, IOGyan]
 2 An updated vector elements :[thanks, Welcome, to, IOGyan]

Vector method addFirst() with custom object

 1 package iogyan.example;
 2 
 3 import iogyan.model.Employee;
 4 
 5 import java.util.Arrays;
 6 import java.util.Vector;
 7 
 8 
 9 public class EmployeeMain {
 10 
 11     public static void main(String[] args) {
 12 
 13         Employee emp1 = new Employee(1, "Emp1","Tech", 1000);
 14         Employee emp2 = new Employee(2, "Emp2","Admin", 5000);
 15         Employee emp3 = new Employee(3, "Emp3","Admin", 12000);
 16 
 17         Vector<Employee> vector = new Vector<>();
 18         vector.addAll(Arrays.asList(emp1, emp3));
 19         System.out.println("An elements of vector : " + vector);
 20 
 21         // add element at first position
 22         vector.addFirst(emp2);
 23         System.out.println("An updated vector elements :" + vector);
 24     }
 25 }

In the above example, a Vector of type Employee created and elements added using addAll() called by passing a collection. A addFirst() method called by passing an employee object that added as first position in this vector and print updated vector elements by calling the Employee class toString() method.

Output

 1 An elements of vector : [Emp1 Tech 1000.0, Emp3 Admin 12000.0]
 2 An updated vector elements :[Emp2 Admin 5000.0, Emp1 Tech 1000.0, Emp3 Admin 12000.0]

Employee class

 1 package iogyan.model;
 2 
 3 public class Employee implements Comparable<Employee> {
 4     private final int id;
 5     private final String name;
 6     private final String dept;
 7     private final double salary;
 8 
 9     public Employee(int id, String name, String dept, double salary) {
 10         this.id = id;
 11         this.name = name;
 12         this.dept = dept;
 13         this.salary = salary;
 14     }
 15 
 16     public int getId() {
 17         return this.id;
 18     }
 19 
 20     public String getName() {
 21         return this.name;
 22     }
 23 
 24     public String getDept() {
 25         return this.dept;
 26     }
 27 
 28     public double getSalary() {
 29         return this.salary;
 30     }
 31 
 32     @Override
 33     public int hashCode() {
 34         return super.hashCode();
 35     }
 36 
 37     @Override
 38     public boolean equals(Object obj) {
 39         return this.id == ((Employee)obj).id;
 40     }
 41 
 42     @Override
 43     public String toString() {
 44         return this.getName() + " " + this.getDept() + " " + this.getSalary();
 45     }
 46 
 47     @Override
 48     public int compareTo(Employee o) {
 49         return this.getId() - o.getId();
 50     }
 51 }