Array of Objects in Java

        

          

            

              
              

          
 
          

          
          

          

            
Introduction to Array of Objects

              

                  
              

          

          

          

            
Sorting an Array of Objects

              

                  
              

          

          

          




Introduction to Array of objects in Java



  
An array of objects in Java is a collection of objects of the same type. It is a more powerful and flexible data structure than a traditional array, which can only store primitive data types.


  
To create an array of objects, you first need to declare an array of object references. Then, you can initialize each element of the array with a new object. For example, the following code creates an array of `Person` objects:


  
    Person[] people = new Person[3];
    people[0] = new Person("Alice", 25);
    people[1] = new Person("Bob", 30);
    people[2] = new Person("Carol", 35);
  


  
Once you have created an array of objects, you can access the elements of the array using the square bracket notation. For example, the following code prints the name of the first person in the `people` array to the console:


  
    System.out.println(people[0].name);
  


  
Output:


  
    Alice
  


  
You can also use loops to iterate over an array of objects. For example, the following code prints the names of all the people in the `people` array to the console:


  
    for (int i = 0; i < people.length; i++) {
      System.out.println(people[i].name);
    }
  


  
Output:


  
    Alice
    Bob
    Carol
  


  
Arrays of objects are a powerful tool that can be used to store and manage data in a variety of ways. For example, you could use an array of objects to store the information for a customer database, the products in an online store, or the students in a class.


  
Here are some of the benefits of using arrays of objects in Java:


  
    
    
  • Flexibility: Arrays of objects can store any type of object, which makes them very flexible.
    • 
    
  • Performance: Arrays of objects can be very efficient for accessing and manipulating data.
    • 
    
  • Reusability: Arrays of objects can be reused in different parts of your program, which can save you time and effort.
    • 
  


  
Arrays of objects are an essential part of Java programming. By understanding the basics of arrays of objects, you can write more efficient and maintainable code.








  


Exercises


Code for creating an array of student objects and invoking its methods



  import java.util.Scanner;
  public class javalabclass 
  {
    public static void main(String args[])
      {
      //declaring an array of objects for a class 
      student[] java = new student[3];
      //allocation of memory for student objects
      for(int i=0;i < java.length;i++)
      {
        java[i]=new student();
      }
      //calling the methods for each object
      for(int i=0;i < java.length;i++)
      {
        java[i].set_profile();
        java[i].view_profile();
      }
          
      }
  }
  
  class student
  {
    
    String regNumber;
    String Name;
    String city;
    
    public void set_profile()
    {
      Scanner input = new Scanner(System.in);
      System.out.println("Enter your regNumber");
      this.regNumber = input.next();
      System.out.println("Enter your Name");
      this.Name = input.next();
      System.out.println("Enter your City");
      this.city=input.next();
      
    }
    
    public void view_profile()
    {
      System.out.println(this.Name+this.regNumber+this.city);
    }
    
  }
  
  Output:
  Enter your regNumber
  112
  Enter your Name
  Prince
  Enter your City
  Vellore
  Prince112Vellore
  Enter your regNumber
  113
  Enter your Name
  Mathew
  Enter your City
  Pune
  Mathew113Pune
  Enter your regNumber
  114
  Enter your Name
  Satish
  Enter your City
  Mumbai
  Satish114Mumbai 




Code for Searching an Array of Student Objects using an input Student Name



  import java.util.Scanner;
  public class javalabclass 
  {
    public static void main(String args[])
      {
      //declaring an array of objects for a class 
      student[] java = new student[3];
      //allocation of memory for student objects
      for(int i=0;i < java.length;i++)
      {
        java[i]=new student();
      }
      //calling the methods for each object
      for(int i=0;i < java.length;i++)
      {
        java[i].set_profile();
        java[i].view_profile();
      }
      //calling the search method
      Scanner input = new Scanner(System.in);
      System.out.println("Enter the name to search");
      String searchName = input.next();
      student.search(java,searchName);
          
      }
  }
  
  class student
  {
    
    String regNumber;
    String Name;
    String city;
    
    public void set_profile()
    {
      Scanner input = new Scanner(System.in);
      System.out.println("Enter your regNumber");
      this.regNumber = input.next();
      System.out.println("Enter your Name");
      this.Name = input.next();
      System.out.println("Enter your City");
      this.city=input.next();
      
    }
    
    public void view_profile()
    {
      System.out.println(this.Name+this.regNumber+this.city);
    }
    
    public static void search(student t[],String inputName)
    {
      boolean found =false;
      for(int i=0;i < t.length;i++)
      {
        if(t[i].Name.equals(inputName))
        {
          System.out.println(t[i].regNumber+t[i].city);
          found=true;
          break;
        }
      }
      if(!found)
      {
        System.out.println("No such student in the array");
      }
    }
  }
  
  Output:
  Enter your regNumber
  112
  Enter your Name
  satish
  Enter your City
  vellore
  satish112vellore
  Enter your regNumber
  113
  Enter your Name
  Prince
  Enter your City
  Mumbai
  Prince113Mumbai
  Enter your regNumber
  114
  Enter your Name
  Mathew
  Enter your City
  Jaipur
  Mathew114Jaipur
  Enter the name to search
  Prince
  113Mumbai 




  Display the details of Employee objects sorted in the ascending order of their name 

  Data Members

  
    
     
  •  Employee ID
    • 
     
  • Name
    • 
     
  •  Date of Birth
    • 
     
  •  Phone
    • 
    

  
  Methods

  
    
     
  •  Set_EmployeeInfo
    • 
      
  • View_Profile
    • 
      
  • Sort_Employee(employee s[]) 



  import java.util.*;
  public class javalabclass{
    public static void main(String args[]){
        System.out.println("Enter the number of employees:");
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        Employee[] a=new Employee[n];
        for(int i=0;i < n;i++)
        {
            a[i]= new Employee();
            System.out.println("For Employee"+(i+1));
            a[i].Set_Employee();
        }
        //sorting the array of employee objects by name
        Employee.sort_employeeName(a);
        //viewing the employee data
        for(int i=0;i < n;i++)
        {
            a[i].View_Employee();
        }
    }
  }
  class Employee{
    public String Employee_id;
    public String Name;
    public int year;
    public int month;
    public int date;
    public String phno;
    public void Set_Employee()
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter the emplyee ID:");
        Employee_id=sc.next();
        System.out.println("Enter the Name:");
        Name=sc.next();
        System.out.println("Enter the year of birth:");
        year=sc.nextInt();
        System.out.println("Enter the month of birth:");
        month=sc.nextInt();
        System.out.println("Enter the date of birth:");
        date=sc.nextInt();
        System.out.println("Enter the phone number:");
        phno=sc.next();
        
    }
      
    public static void sort_employeeName(Employee[] a)
    {
        for(int i=0;i < a.length-1;i++)
          {
              for(int j=i+1;j < a.length;j++){
                  if((a[i].Name).compareTo(a[j].Name)>0){
                      Employee temp;
                      temp=a[i];
                      a[i]=a[j];
                      a[j]=temp;
                  }
              }
          }
    }
    
    public void View_Employee()
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("The Employee ID is: "+Employee_id);
        System.out.println("The Employee Name is: "+Name);
        System.out.println("The Employee year of birth: "+year);
        System.out.println("The Employee month of birth: "+month);
        System.out.println("The Employee date of birth: "+date);
        System.out.println("The Employee phone number: "+phno);
    }
  }
  
  Output:
  Enter the number of employees:
  3
  For Employee1
  Enter the emplyee ID:
  112
  Enter the Name:
  Mohan
  Enter the year of birth:
  2001
  Enter the month of birth:
  0
  Enter the date of birth:
  12
  Enter the phone number:
  8799999
  For Employee2
  Enter the emplyee ID:
  113
  Enter the Name:
  Anbu
  Enter the year of birth:
  2002
  Enter the month of birth:
  3
  Enter the date of birth:
  12
  Enter the phone number:
  767777
  For Employee3
  Enter the emplyee ID:
  114
  Enter the Name:
  pratap
  Enter the year of birth:
  2000
  Enter the month of birth:
  4
  Enter the date of birth:
  11
  Enter the phone number:
  78888
  The Employee ID is: 113
  The Employee Name is: Anbu
  The Employee year of birth: 2002
  The Employee month of birth: 3
  The Employee date of birth: 12
  The Employee phone number: 767777
  The Employee ID is: 112
  The Employee Name is: Mohan
  The Employee year of birth: 2001
  The Employee month of birth: 0
  The Employee date of birth: 12
  The Employee phone number: 8799999
  The Employee ID is: 114
  The Employee Name is: pratap
  The Employee year of birth: 2000
  The Employee month of birth: 4
  The Employee date of birth: 11
  The Employee phone number: 78888 




 Search the array of Employee objects to display the names of Employees who will retire after 2030 if the retirement age for an employee is 58 years. 

  Data Members

  
    
     
  •  Employee ID
    • 
     
  • Name
    • 
     
  •  Date of Birth (Get Year , Month and Day as integers)
    • 
     
  •  Phone
    • 
    

  
  Methods

  
    
     
  •  Set_EmployeeInfo
    • 
      
  • View_Profile
    • 
      
  • View_RetirementInfo(employee s[]) 



  import java.util.*;
  public class javalabclass{
  public static void main(String args[]){
      System.out.println("Enter the number of employees:");
      Scanner sc=new Scanner(System.in);
      int n=sc.nextInt();
      Employee[] a=new Employee[n];
      for(int i=0;i < n;i++)
      {
          a[i]= new Employee();
          System.out.println("For Employee"+(i+1));
          a[i].Set_Employee();
      }
      //Viewing Employees who will retire after 2030
      Employee.view_retirementInfo(a);        
  }
  }
  class Employee{
  public String Employee_id;
  public String Name;
  public int year;
  public int month;
  public int date;
  public String phno;
  public void Set_Employee()
  {
      Scanner sc=new Scanner(System.in);
      System.out.println("Enter the emplyee ID:");
      Employee_id=sc.next();
      System.out.println("Enter the Name:");
      Name=sc.next();
      System.out.println("Enter the year of birth:");
      year=sc.nextInt();
      System.out.println("Enter the month of birth:");
      month=sc.nextInt();
      System.out.println("Enter the date of birth:");
      date=sc.nextInt();
      System.out.println("Enter the phone number:");
      phno=sc.next();
      
  }
    
  public static void view_retirementInfo(Employee[] s)
  {
    boolean found = false;
    System.out.println("Employees retiring after 2030");
    for(int i=0;i < s.length;i++)
    {
      if((s[i].year+58)>2030)
      {
        System.out.println(s[i].Name+" "+s[i].phno);
        found=true;
      }
      
    }
    if(!found)
    {
      System.out.println("No Employees will retire after 2030");
    }
        
  }
  
  public void View_Profile()
  {
      Scanner sc=new Scanner(System.in);
      System.out.println("The Employee ID is: "+Employee_id);
      System.out.println("The Employee Name is: "+Name);
      System.out.println("The Employee year of birth: "+year);
      System.out.println("The Employee month of birth: "+month);
      System.out.println("The Employee date of birth: "+date);
      System.out.println("The Employee phone number: "+phno);
  }
  }
  
  
  Output:
  Enter the number of employees:
  3
  For Employee1
  Enter the emplyee ID:
  11
  Enter the Name:
  Satish
  Enter the year of birth:
  1940
  Enter the month of birth:
  0
  Enter the date of birth:
  1
  Enter the phone number:
  766777
  For Employee2
  Enter the emplyee ID:
  12
  Enter the Name:
  Ram
  Enter the year of birth:
  2020
  Enter the month of birth:
  2
  Enter the date of birth:
  14
  Enter the phone number:
  6578877
  For Employee3
  Enter the emplyee ID:
  13
  Enter the Name:
  Prince
  Enter the year of birth:
  2021
  Enter the month of birth:
  0
  Enter the date of birth:
  21
  Enter the phone number:
  566777
  Employees retiring after 2030
  Ram 6578877
  Prince 566777