import java.util.*;

PVector pv;
LinkedList list;
int nbrToRemember = 10;

void setup(){
  list = new LinkedList();

  // simulate movement from 0,0,0 to 99,99,99
  for(int i = 0; i < 100; i++){
    pv = new PVector(i,i,i);
    addNewPosition(pv);
  }
  displayList();
}

// Add a new PVector but only remeber the last 'nbrToRemember'
void addNewPosition(PVector p){
  list.addFirst(p);
  while(list.size() > nbrToRemember)
    list.removeLast();
}

// Loop through the vetors and do something with them
// this could be part of your draw() method
void displayList(){
  PVector tempPv;
  ListIterator iter = list.listIterator();
  while(iter.hasNext()){
    tempPv = (PVector)iter.next();
    println(tempPv);
  }
}