Arraylist help.

[puchatek]

Hello, I created an Arraylist to hold multiple classrooms. However I'm stuck with how to add a teacher in my School class, to a classroom by using the classrooms arraylist parameter (such as 0,1,2 etc)

public class classroom
{
    private String classRoomName;
    private String teacherName;
    
    public void setClassRoomName(String newClassRoomName)
    {
        classRoomName = newClassRoomName;

    }
    
    public String returnClassRoomName()
    {
        return classRoomName;
    }
    
    public void setTeacherName(String newTeacherName)
    {
        teacherName = newTeacherName;

    }
    
    public String returnTeacherName()
    {
        return teacherName;
    }
}

import java.util.ArrayList;

public class School
{
    private ArrayList<classroom> classrooms;
    private String classRoomName;
    private String teacherName;
    
    public School()
    {
        classrooms =  new ArrayList<classroom>();
    }

    public void addClassRoom(classroom newClassRoom, String theClassRoomName)
    {
        classrooms.add(newClassRoom);
        classRoomName = theClassRoomName;
    }

    // how to write a method to add a teacher to the classroom by using the classroom parameter
    // and the teachers name
}

[Eranga]

Do you want to keep a map with the classroom and teacher assign to it?

[puchatek]

Do you want to keep a map with the classroom and teacher assign to it?

Not for now. I just want to add a teacher to the correct array e.g. array 0.
Im still very new to java lol
Thanks

[Eranga]

array 0 means that you want to add in a specific index of the ArrayList? Could you please clarify that.

Here in the following code segment,

public void addClassRoom(classroom newClassRoom, String theClassRoomName)
    {
        classrooms.add(newClassRoom);
        classRoomName = theClassRoomName;
    }

you've added classroom object to the end of the ArrayList always.

[puchatek]

array 0 means that you want to add in a specific index of the ArrayList? Could you please clarify that.

Here in the following code segment,

public void addClassRoom(classroom newClassRoom, String theClassRoomName)
    {
        classrooms.add(newClassRoom);
        classRoomName = theClassRoomName;
    }

you've added classroom object to the end of the ArrayList always.

Yup, I want to add a teacher to a specific index of an Arraylist.
So e.g. I create.
0 - History Classroom
1 - Maths Classroom
2 - Science Classroom
And I would like to add Mr Puchatek to 2 the science class.

Sorry I'm very bad at explaining what I need lol.
Thanks, Puchatek

[Eranga]

Then look at add(Object obj, int index) in array class.

0 - History Classroom
1 - Maths Classroom
2 - Science Classroom

I hope the above three are different arrays, is it?

[puchatek]

Then look at add(Object obj, int index) in array class.



I hope the above three are different arrays, is it?

Yup they are different arrays.

How would I have to write?

add(Object obj, int index)

to add a teacher?

Thanks

[Eranga]

Same as follows,

classrooms.add(newClassRoom);

additionally you've to specify the index you want to store the object.

classrooms.add(newClassRoom, 1);
classrooms.add(newClassRoom, 2);

[Eranga]

ArrayList (Java 2 Platform SE v1.4.2)

[Eranga]

Sorry about that I've added arguments in incorrect order. It should be like this,

add(int index, Object obj);

Please check with the above link.

[puchatek]

Thank you for your help.

As I don't want to make another topic. I want to write a method in the School class to call the method setTeacherName in the classroom class. How do I do this?

Thanks

[Eranga]

Define a method in School class which you want to invoke by. Then create an object of Classroom class within it, and invoke the method, which is public.