Hello, I have this code right here which uses threads to sort the given ArrayList. Can someone help me fix the mergeSort and merge method here because it will not compile nor run giving me an "Exception in thread "main" java.lang.StackOverflowError"

note: The Employee class is nothing special. Just a bunch of set and get methods for ID and salary.

Code

import java.util.ArrayList; import java.util.List; import java.util.Random;

public class ThreadSorting { public static void main(String[] args) { // TODO Auto-generated method stub ArrayList list1; ArrayList list2; long nextID = 0; ArrayList empList = new ArrayList(10000); //sort 10000 elements for (int i = 0; i < 10000; i++) { nextID++; Employee e = new Employee(nextID, getSalary());//fil with random ID and salary from the Employee class empList.add(e); // System.out.println(e.getID() + " " + e.getSalary()); } list1 = new ArrayList(); list2 = new ArrayList(); for (int i = 0; i < empList.size()/2; i++) { list1.add(empList.get(i)); //fill the first half of the empList } for (int i = 0; i < empList.size() - empList.size()/2; i++) { list2.add(empList.get(i)); //fill the second half of the empList } Thread thr1 = new Thread(new Runnable() { public void run() { function1(list1); //thread takes care of function 1 } }); Thread thr2 = new Thread(new Runnable() { public void run() { function2(list2); //takes care of function 2 } }); thr1.start(); thr2.start(); } public static void function1(ArrayList list1) { mergeSort(list1); }

public static void function2(ArrayList list2) { mergeSort(list2); }

public static void mergeSort(ArrayList list1){ ArrayList left = new ArrayList(); ArrayList right = new ArrayList(list1.size() - list1.size()/2); for (int i = 0; i < list1.size()/2; i++) { left.add(list1.get(i)); } for (int i = 0; i < list1.size() - list1.size()/2; i++) { right.add(list1.get(i)); } mergeSort(left); //right here is the problem mergeSort(right); //problem I'm getting merge(list1, left, right); } public static void merge(ArrayList list1, ArrayList left, ArrayList right) { int i = 0, j = 0; ArrayList temp = new ArrayList(); while(i < left.size() && j < right.size()) { if (left.get(i).getSalary() < right.get(j).getSalary()) { temp.add(left.get(i)); i++; } else { temp.add(right.get(j)); j++; } } while (i <= left.size()) { temp.add(left.get(i)); i++; } while( j > right.size()) { temp.add(right.get(j)); j++; } } public static int getSalary() { Random r = new Random(); return r.nextInt((4000-1500)+1)+1600; } }