Question

Create a Java program that will store 10 student objects in an ArrayList, ArrayList<Student>. A student object consists of the following fields:

• int rollno
• String name
• String address

Implement two comparator classes to sort student objects by name and by rollno (roll number). Implement your own selection sort method and place your code in a separate Java source file. Do not use a sort method from the Java collections library.

Answer 1

CODE

import java.util.ArrayList;

import java.util.Comparator;

import java.util.Random;

class Student {

int rollno;

String name;

String address;

public Student(int rollno, String name, String address) {

super();

this.rollno = rollno;

this.name = name;

this.address = address;

}

@Override

public String toString() {

return "Student [rollno=" + rollno + ", name=" + name + ", address=" + address + "]";

}

}

class Sortbyroll implements Comparator<Student>

{

// Used for sorting in ascending order of

// roll number

public int compare(Student a, Student b)

{

return a.rollno - b.rollno;

}

}

class Sortbyname implements Comparator<Student>

{

// Used for sorting in ascending order of

// roll name

public int compare(Student a, Student b)

{

return a.name.compareTo(b.name);

}

}

public class Main {

public static void sort(ArrayList<Student> students)

{

Sortbyroll sortbyroll = new Sortbyroll();

int n = students.size();

// One by one move boundary of unsorted subarray

for (int i = 0; i < n-1; i++)

{

// Find the minimum element in unsorted array

int min_idx = i;

for (int j = i+1; j < n; j++)

if (sortbyroll.compare(students.get(j), students.get(min_idx)) < 0)

min_idx = j;

// Swap the found minimum element with the first

// element

Student temp = students.get(min_idx);

students.set(min_idx, students.get(i));

students.set(i, temp);

}

}

public static void main(String[] args) {

Random rand = new Random();

ArrayList<Student> students = new ArrayList<>();

for (int i=0; i<10; i++) {

int roll = rand.nextInt(100);

String name = "Name" + i;

String address = "Address" + i;

students.add(new Student(roll, name, address));

}

sort(students);

System.out.println("The sorted students are:");

for (Student s : students) {

System.out.println(s);

}

}

}

​​​​​​​

? Problems @ Javadoc Declaration Search Console X sterminated> StackListBased [Java Application] /Library/Java/JavaVirtualMa The sorted students are: Student [rollno-8, name-Name9, address-Address9] Student [rollno-20, name-Name7, address-Address7] Student [rollno-24, name-Name6, address-Address6] Student [rollno-27, name-Name8, address-Address8] Student [rollno-29, name-Name0, address-Address0] Student [rollno-55, name-Name1, address-Address1] Student [rollno-62, name-Name4, address-Address4] Student [rollno-78, name-Name5, address-Address5] Student [rollno-91, name-Name3, address-Address3] Student [rollno-91, name-Name2, address-Address2]