单独的集合类对象

Question

My project involves 2 classes: Members & Society .

Currently I have written a method ' removeMembers() ' in the Society Class that when given a particular month and year, it removes all the members who fit the description.

However, how would I create a separate collection class object which returns the deleted members?

Any help or advice on this will be appreciated, I will also post my code for both classes.

Society Class:

public class Society
{
   private ArrayList<Member> myMembers;
   private Member member;
   private String societyName;
   private boolean feesPaid;


   public Society(String society)
   {
      myMembers = new ArrayList<Member>();
      this.societyName = society;
   }

   public String getSocietyName()
   {
     return societyName;  
   }

   public void join(Member member)
   {
      myMembers.add(member);
   }

   public void showMember(int listPosition)
   {
      Member member;
      if( listPosition < myMembers.size() )
      {
         member = myMembers.get(listPosition);
         System.out.println("Position " + listPosition  + ": " + member);
      }
   }

   public void joinedInMonth(int joined) {
        if (joined > 12 || joined < 1) {
            System.out.println("Invalid number. Please enter a number from 1 - 12.");       
       }
       long joinedMonth = myMembers.stream().filter(m -> m.getMonth() == joined).count();
       System.out.printf("%d members have joined this society on month %d%n", joinedMonth, joined);

   }

   public int numberOfMembers()
   {
      return myMembers.size();
   }

   public void printDetails()
   {
       for (Member m : myMembers) {
      System.out.println("Society Name: " + societyName);
      System.out.println(m.toString());
      System.out.println("--------------------------");
     } 

   }

   public void removeMembers(int month, int year) {
    myMembers.removeIf(m -> m.getYear() == year && m.getMonth() == month);
   }

   public void payFees(Member member)
    {
      if (member.isFeesPaid()) {
        System.out.println("Fees has been paid");
        return;
    }
   }
}

Member Class:

public class Member
{

   private int month;
   private int year;
   private String name;
   /*private Society society;*/
   private List<Society> societies;
   private boolean feesPaid;
   public Member(String name, int month, int year /*Society society*/)
   {
      this.name  = name;
      this.month = month;
      this.year = year;
      this.societies = new ArrayList<>();
   }

   public void joinSociety(Society society)
   {
       societies.add(society);
    }

   public boolean isFeesPaid() {
    return feesPaid;
    }

   public int getYear()
   {
    return year;
   }

   public int getMonth()
   {
     return month;
   }

   public String getName()
   {
     return name;
   }

   public String toString()
   {
     return "Name: " + name + ", Month Joined: " + month + ", Year Joined: " + year;
   }

Answer 1

You can create a new List in removeMembers() method and add the removed objects to list and return it. remove(Object o) method in arraylist will return the removed object and remaining methods remove(int index) , removeIf(Predicate<? super E> filter) and removeRange(int fromIndex, int toIndex) will not return removed object

public List<Members> removeMembers(int month, int year) {
   List<Members> deletedMembers= new ArrayList<>();
    Iterator<Members> members = myMembers.iterator();
    while (members.hasNext()) {
        Member member = members.next();
        if (member.getYear()==year && member.getMonth()==month) {
           deletedMembers.add(members.remove());
        }
    }
    return deletedMembers;
}