Question

A Lecturer wishes to create a program that lists his students sorted by the number of theory assignment marks they have completed. The listing should be greatest number of assignment first, sub-sorted by name in lexicographical order (A to Z). A class Student stores the name and marks of assignment completed for a student.                                                    [5 marks]

Note: Assume the variable name of collection is list.

      i.         Provide a definition of Student with an equals() method. The comparison is based on name of the student.                                                                                     [3 marks]

    ii.         Write java statement to declare a collection variable list of type Student             [2 marks]

   iii.         Implements interface Comparator such that fulfil a natural ordering that matches the given requirement. Define method compareTo() such that it compares based on greatest number of assignment first, sub-sorted by name in lexicographical order (A to Z)). [5 marks]

   iv.         Provide definition of find(String) method which returns the index if given name exists in collection.                                                                                                     [2 marks]

     v.         Provide a static method in application class to display all students by calling toString method. Assume the name of object of collection is list.                             [4 marks]

Answer 1

Application class:

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class Application {
   public static void main(String[] args) {
       List<Student> list = new ArrayList<Student>();
       list.add(new Student("sai",90));
       list.add(new Student("kumar",85));
       list.add(new Student("abhilash",74));
       list.add(new Student("venkat",68));
       list.add(new Student("jay",90));
       list.add(new Student("alex",60));
       list.add(new Student("jonas",90));
       list.add(new Student("magnus",57));
       Collections.sort(list);
       Iterator iterator = list.iterator();
       while(iterator.hasNext()) {
       System.out.println(iterator.next());
       }
   }

}

Student class:

import java.util.Comparator;

public class Student implements Comparable<Student> {
  
   private String name;
   private int marks;

   public Student(String name, int marks) {
       super();
       this.name = name;
       this.marks = marks;
   }

   @Override
   public boolean equals(Object obj) {
       if (this == obj)
           return true;
       if (obj == null)
           return false;
       if (getClass() != obj.getClass())
           return false;
       Student other = (Student) obj;
       if (marks != other.marks)
           return false;
       if (name == null) {
           if (other.name != null)
               return false;
       } else if (!name.equals(other.name))
           return false;
       return true;
   }

   @Override
   public int compareTo(Student s2) {
       if (this.marks < s2.marks)
           return 1;
           else if (this.marks > s2.marks)
           return -1;
           else
           {
           if((this.name).compareToIgnoreCase(s2.name)<0)
           return -1;
           else if((this.name).compareToIgnoreCase(s2.name)>0)
           return 1;
           else
           return 0;
           }
   }
  
  
  
  
   @Override
   public String toString() {
   return "Student [name=" + name + ", marks=" + marks + "]";
   }   
     

}

output:

1.public class Student {

   String name;
   int marks;
  
   @Override
   public boolean equals(Object obj) {
       if (this == obj)
           return true;
       if (obj == null)
           return false;
       if (getClass() != obj.getClass())
           return false;
       Student other = (Student) obj;
       if (name == null) {
           if (other.name != null)
               return false;
       } else if (!name.equals(other.name))
           return false;
       return true;
   }
  

}

2.List<Student> list = new ArrayList<Student>();

3.class StudentComparator implements Comparator<Student>{
  
  
public int compare(Student s1, Student s2) {
if (s1.marks < s2.marks)
return 1;
else if (s1.marks > s2.marks)
return -1;
               else
{
if((s1.name).compareToIgnoreCase(s2.name)<0))
                   return -1;
                   else if((s1.name).compareToIgnoreCase(s2.name)>0))
                   return 1;
}
               return 0;  
}
}
      
      
4. int position = students.indexof(name)

5.ToString method:
@Override
   public String toString() {
       return "Student [name=" + name + ", marks=" + marks + "]";
   }
  
Printing all students:

       Collections.sort(list);
       Iterator iterator = list.iterator();
       while(iterator.hasNext()) {
       System.out.println(iterator.next());
       }
  

}