Many-many

1.       Many-To-Many Association:-

It is a relationship between entity classes, where multiple instance of an entity should mapped with multiple instance of another entity.

Ex:-

Multiple students have joined with multiple Courses.

Ex code:-

class Course

{

                String cid;

                String cname;

                int ccost;

                Course(String cid, String cname, int ccost)

                {

                                this.cid=cid;

                                this.cname=cname;

                                this.ccost=ccost;

                }

}

class Student

{

                String sid;

                String sname;

                String saddr;

                Course[] crs;

                Student(String sid, String sname, String saddr, Course[] crs)

                {

                                this.sid=sid;

                                this.sname=sname;

                                this.saddr=saddr;

                                this.crs=crs;

                }

                public void getStudentDetails()

                {

                                System.out.println("Student Details");

                                System.out.println("--------------------");

                                System.out.println("Student Id      :"+sid);

                                System.out.println("Student Name    :"+sname);

                                System.out.println("Student Address :"+saddr);

                                System.out.println("CID\tCNAME\tCCOST");

                                System.out.println("----------------------");

                                for(int i=0;i<crs.length;i++)

                                {

                                                Course c=crs[i];

                                                System.out.println(c.cid+"\t"+c.cname+"\t"+c.ccost);

                                }

                                System.out.println();

                }

}

class ManyToManyEx

{

                public static void main(String[] args)

                {

                                Course c1=new Course("C-111","C",1000);

                                Course c2=new Course("C-222","C++",2000);

                                Course c3=new Course("C-333","JAVA",5000);

                                Course[] crs={c1,c2,c3};

                                Student std1=new Student("S-111","AAA","Hyd",crs);

                                Student std2=new Student("S-222","BBB","Hyd",crs);

                                Student std3=new Student("S-333","CCC","Hyd",crs);

                                std1.getStudentDetails();

                                std2.getStudentDetails();

                                std3.getStudentDetails();

                }

}

Output :-

Student Details

---------------

Student Id     :S-111

Student Name   :AAA

Student Address:Hyd

CID CNAME CCOST

---------------

C-111 C   1000

C-222 C++ 2000

C-333 JAVA5000

Student Details

---------------

Student Id     :S-222

Student Name   :BBB

Student Address:Hyd

CID CNAME CCOST

---------------

C-111 C   1000

C-222 C++ 2000

C-333 JAVA5000

Student Details

---------------

Student Id     :S-333

Student Name   :CCC

Student Address:Hyd

CID CNAME CCOST

---------------

C-111 C   1000

C-222 C++ 2000

C-333 JAVA5000

Data Flow of execution :-