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Association in Java Programming

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What is Association in java


  • Relationship between one or more classes
  • Aggregation and composition is a special type of association


 For example, Student Belongs to a specific Faculty and One faculty has many students

 Code Example:

class Student {
  String name;
  Student () {name=null; }
  Student (String n) {name=n; }
  void setName(String n) {name=n;}
  String getName() { return name;}
}
class Faculty{
  Student student[];
  int size;
  Faculty (int s){size=0;
           student=new Student[s];}
void belongsTo(Student p){
    student[size]=p;
    size++;
}
void print(){
   for (int i=0;i<size;i++)
      System.out.println(student[i].getName());
}
}
class Test{
public static void main (String a[]){
    Faculty FIT= new Faculty(5);
    Faculty FMS= new Faculty(5);
    
    Student s1=new Student("Hamza");
    FMS.belongsTo(s1);
    
    Student s2=new Student("Kamil");
    FIT.belongsTo(s2);
    
    Student s3=new Student("Shoaib");
    FMS.belongsTo(s3);
    
    System.out.println("FIT students");
    FIT.print();
    System.out.println("FMS students");
    FMS.print();
    }
}






Practice 2

  • Student register for one or more courses
  • One student can register max 5 courses
  • Each course may have a maximum of 50 registered students


class Student {
String name;
Student () {name=null; }
Student (String n) {name=n; }
void setName(String n) {name=n;}
String getName() { return name;}
}
class Course {
String title;
Course  () {title=null; }
Course  (String n) {title=n; }
void setTitle(String n) {title=n;}
String getTitle() { return title;}
}

class Registration{
Student s;
Course  c;
void register(Student s,Course c ) {
            this.s=s;
            this.c=c;
}
void print(){
 System.out.print(s.getName() + " Register ");
 System.out.println(c.getTitle());
}
}

class Test{
public static void main (String a[]){
Registration r[]=new Registration[10];
Student s1= new Student("Jhon");
Student s2= new Student("Alex");
Student s3= new Student("Jawad");
Course  c1 = new Course ("DSA");
Course  c2 = new Course ("Algo");
r[0] = new Registration();
r[0].register(s1,c1);
r[1] = new Registration();
r[1].register(s2,c1);
r[2] = new Registration();
r[2].register(s3,c2);
r[3] = new Registration();
r[3].register(s1,c2);
for (int i=0;i<4;i++)
   r[i].print();

}
}

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