Association Relationship in Java

        

          

            

              
              

          
 
          

          
          

          

              

                  
              

          








Introduction to Association Relationship between Classes in Java



An association relationship between classes in Java is a relationship where two classes are aware of each other and can interact with each other. This type of relationship is often used to model real-world relationships, such as the relationship between a customer and an order, or the relationship between a student and a course.



Association relationships can be one-to-one, one-to-many, many-to-one, or many-to-many.



    
  
  • One-to-one association relationship: A one-to-one association relationship means that one object in one class can only be associated with one object in the other class. For example, a customer can only have one order at a time.
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  • One-to-many association relationship: A one-to-many association relationship means that one object in one class can be associated with multiple objects in the other class. For example, a customer can have many orders.
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  • Many-to-one association relationship: A many-to-one association relationship means that multiple objects in one class can be associated with one object in the other class. For example, many students can be enrolled in one course.
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  • Many-to-many association relationship: A many-to-many association relationship means that multiple objects in one class can be associated with multiple objects in the other class. For example, many students can take many courses.
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Association relationships can be implemented in Java using fields, methods, or both. For example, the following code shows a one-to-one association relationship between a `Customer` class and an `Order` class:




public class Customer {
  private Order order;

  public Order getOrder() {
    return order;
  }

  public void setOrder(Order order) {
    this.order = order;
  }
}

public class Order {
  private Customer customer;

  public Customer getCustomer() {
    return customer;
  }

  public void setCustomer(Customer customer) {
    this.customer = customer;
  }
}




In this example, the `Customer` class has a field called `order` that stores a reference to an `Order` object. The `Order` class has a field called `customer` that stores a reference to a `Customer` object.



Association relationships are a powerful tool for modeling real-world relationships in Java. By using association relationships, you can write more robust and reliable code.



Here are some tips for using association relationships effectively:



    
  
  • Choose the right type of association relationship for the relationship you are modeling.
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  • Use fields or methods to implement association relationships, depending on your specific needs.
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  • Document the association relationships in your code so that it is clear how the classes are related to each other.
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Exercises


Demo code for Association Relationship between classes in Java



  package sampleproject;
  import java.util.Scanner;
  
  public class democlass {
  
    public static void main(String[] args) {
      
      student s1 = new student("satish","12BCE","99456");
      professor p = new professor();
      p.viewprofile(s1);
    }
  }
  
  class student
  {
    String name;
    String regno;
    String phone;
    
    public student(String name, String regno, String phone) {
      super();
      this.name = name;
      this.regno = regno;
      this.phone = phone;
    }
  
    public String getInfo() {
            return(name+regno+phone);	
    }
  }
  
  class professor
  {
    public void viewprofile(student s1) 
    {
      System.out.println("Enter student id");
      Scanner input = new Scanner(System.in);
      String regno=input.nextLine();
      if(s1.regno.equals(regno))
      {
        System.out.println(s1.getInfo());
      }
    }
  }