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package com.java;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

import java.util.Objects;

import java.util.concurrent.CopyOnWriteArrayList;

import java.util.stream.Collectors;

//The real cause of ConcurrentModfiicationException is inconsistent modCount.

// When you are iterating over ArrayList then Iterator's next() method keep track of modCount.

// If you modify the collection by adding or removing elements then modCount will change and

// it will not match with the expected modCount,

// hence Iterator will throw ConcurrentModificationException.

//Solution: Use Iterator if you are doing it on the single-threaded environment,

// otherwise use concurrent collection classes

// e.g. CopyOnWriteArrayList to remove elements while you are looping over it.

public class ConcurrentModification {

public static void main(String args[]) {

List<Integer> integers = new ArrayList<Integer>();

integers.add(1);

integers.add(2);

integers.add(3);

for (Integer integer : integers) { //thows in this place

//integers.remove(1);

}

for (Iterator<Integer> iterator = integers.iterator(); iterator.hasNext();) {

Integer integer = iterator.next();

if(integer == 2) {

iterator.remove();

}

}

List<Integer> integerss = new CopyOnWriteArrayList<Integer>();

integers.add(1);

integers.add(2);

integers.add(3);

integerss.removeIf(i -> i == 2);

integers.stream().filter(i -> i!=2).map(Objects::toString).collect(Collectors.toList());

}

}