Thread: Arraylist removing element

Hi

i have an arraylist thats keeping a track of members, i need to remove a member and have the list push all other elements down by 1. Please help

 
ArrayList<Membership> member;
 ArrayList<Books> book;
 private int nextMemberID;
 private int nextBookId;
    /**
     * Constructor for objects of class Library
     */
    public Library() 
    {
 
       nextMemberID = 1;
       nextBookId = 1;
 
       member = new ArrayList<Membership>();
       book = new ArrayList<Books>();
 
 
    }
 
 
 
 
 
public void removeMember(int ID) {
    //First we find the lot with the given number
    Membership membership = getMember(ID);
    if (membership != null) {
        //Then we can use the method remove with lot as argument
       member.remove(membership);
       nextMemberID--;
 
    }
 
}

sorry i didn't mean the element because they do move down as you remove objects, i meant to get my "nextMemberID" to shuffle down by 1 so as to fill the gap.

I'm not sure what the question really is...it seems your code removes an element, and decrements a marker. I'd suggest an SSCCE to more clearly demonstrate the behavior you get vs the behavior you want.

Ok i can see my question isn't clear so i'll try to explaine. if i add 10 members to the array then the array will hold these members in cells 0-9. My "nextMemberID" will hold these members as 1-10.

If i remove a member (say member 3) then the array will hold them as 0-8 but my "nextMemberID" will have a gap in the number line where 3 was

e.g 1-2 4-10.

Now my nextMemberID-- means that the next member i input will go into array cell 9 but nextMeberID cell 10 which is already in use.

Hope this helps.

Still confused so you'll have to clarify with either a better code example or description. I have no idea what your nextMemberID is used for (its an int, so how can it have a gap?), but based upon its name and description presume all you want it to do is represent member.size() + 1 ?

Here is how i add a member, When i add a member it adds one to the nextMemberID int. So if i add member 4 to the list of 3 members then i'll have 4 members 1,2,3,4. If i remove member 2 then i'll have 1,3,4 but i dont want it to hold the numbers like this, i need the numbers to move down so when i print them it will have their numbers as 1,2,3.

if i have 4 members then the next MemberID number will be 5, but if i remove a member then it will drop the next MemeberID number to 4 but i will still have members 1,3,4. So the next time i add a member it will want to add a MemberID of 4 so i end up with 1,3,4,4.

   public void addnewMember( String first, String last, String telephone)
    {
 
    member.add(new Membership(nextMemberID,first,last,telephone));
    nextMemberID++; 
}

 
public class Membership
{
 
    private String firstName;
    private String lastName;
    private String telephoneNumber;
    private int ID;
 
 
    /**
     * Constructor for objects of class Member
     */
    public Membership(int ID, String first, String last, String telephone)
    {
       this.ID = ID;
       this.firstName = first;
       this.lastName = last;
       this.telephoneNumber = telephone;
 
 
    }
 
    /**
     * @return The member's number.
     */
    public int getID()
    {
        return ID;
    }

all depends on what u want. Do u want the ID to represent the position in list of members? Do u want same ID not to be used twice or more (after removing ID 2 not to have it used again)? Or u want removed ID to be used again?