This is a Java Question, never worked with Maps in Java, and trying to figure th

Question

This is a Java Question, never worked with Maps in Java, and trying to figure this out:

Instructions:

Create a class MyClass with fields : name and numOfStudentsEnrolled.

3)Let classMap be a map for all the classes you enrolled. Using Java, show how to output all of the classes you enrolled using classMap. You should do this by iterating over all of the classes in the map. Output the total number of the classes.

3)When you iterate over all of the classes in 2) you create a ArrayList and add each class to this list.

Output the result.

And then add some more classes, delete some classes and then output the result.

This is what i have so far, not very far into it.

import java.util.Map;

import java.util.HashMap;

public class MyClass {

private String name;

private int numOfStudentsEnrolled;

public String getName() {

return name; }

public int getnumOfStudentsEnrolled() {

return numOfStudentsEnrolled;

}

public void setName(String name) {

this.name = name; }

public void setnumOfStudentsEnrolled() {

this.numOfStudentsEnrolled = numOfStudentsEnrolled; }

public static void main (String[] args) {

map map= new HashMap();

map.put("Java", 100);

map.put("Statistics", 100);

for(Map.Entry m:map.entrySet()) {

System.out.println(m.getKey()+" "+m.getValue());

}

}

}

Explanation / Answer

package javaapplication5;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Set;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.Map.Entry;

class MyClass

{

String name;

int numOfStudentsEnrolled;

static int i=1;

public MyClass(String name, int numOfStudentsEnrolled)

{

this.name=name;

this.numOfStudentsEnrolled=numOfStudentsEnrolled;

}

String getName()

{

return name;

}

int getNoOfStudentsEntrolled()

{

return numOfStudentsEnrolled;

}

void display()

{

System.out.println(" "+name+" "+numOfStudentsEnrolled);

  

}

  

}

public class JavaApplication5 {

/**

* @param args the command line arguments

*/

static Map classMap;

static ArrayList classlist;

static Set< Map.Entry<Integer,MyClass> > st;

static MyClass m;

  

public static void main(String[] args) {

// TODO code application logic here

Map classMap=new HashMap();

  

classMap.put(1,new MyClass("FE",200));

classMap.put(2,new MyClass("SE",300));

classMap.put(3,new MyClass("TE",400));

classMap.put(4,new MyClass("BE",500));

MyClass m1=new MyClass("ME",18);

classMap.put(5,m1);

MyClass m2=new MyClass("diploma",180);

classMap.put(5,m2);

Set< Map.Entry<Integer,MyClass> > st = classMap.entrySet();

System.out.println("Sr. No Name of class No.of Students Enrolled");

ArrayList classlist=new ArrayList();

//Adding and displaying from ArrayList

for (Map.Entry<Integer,MyClass> me:st)

{

System.out.print(me.getKey());

m=me.getValue();

m.display();

String classname=m.getName();

classlist.add(classname);

}

System.out.println("Total no. of classes"+ classMap.size());

System.out.println(classlist);

MyClass m3=new MyClass("PHD",10);

classMap.put(6,m3);

//Adding and displaying from ArrayList

for (Map.Entry<Integer,MyClass> me:st)

{

System.out.print(me.getKey());

m=me.getValue();

m.display();

String classname=m.getName();

if(!classlist.contains(classname))

classlist.add(classname);

}  

System.out.println(classlist);

  

  

System.out.println(classlist);

classMap.remove(3);

  

  

//Adding and displaying from ArrayList

for (Map.Entry<Integer,MyClass> me:st)

{

System.out.print(me.getKey());

m=me.getValue();

m.display();

String classname=m.getName();

if(!classlist.contains(classname))

classlist.add(classname);

}   

  

  

}

}

output:-

Sr. No Name of class No.of Students Enrolled

1 FE 200

2 SE 300

3 TE 400

4 BE 500

5 diploma 180

Total no. of classes5

[FE, SE, TE, BE, diploma]

1 FE 200

2 SE 300

3 TE 400

4 BE 500

5 diploma 180

6 PHD 10

[FE, SE, TE, BE, diploma, PHD]

[FE, SE, TE, BE, diploma, PHD]

1 FE 200

2 SE 300

4 BE 500

5 diploma 180

6 PHD 10

BUILD SUCCESSFUL (total time: 1 second)

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