Sometimes we want to add or remove elements from the list if we find some specific element, in that case we should use concurrent collection class – CopyOnWriteArrayList. So basically iterator throws ConcurrentModificationException if list size is changed. This explains why we don’t get exception if we use set method to replace any existing element.
expectedModCount is the iterator variable that is initialized when we create iterator with same value as modCount. Here modCount is the ArrayList variable that holds the modification count and every time we use add, remove or trimToSize method, it increments. Throw new ConcurrentModificationException()
If you will look into the ArrayList source code, following method is called everytime we invoke next() on iterator that throws exception. Syntax: public boolean add (Object obj) // Appends the specified element to the end of this list.
ARRAY VS ARRAYLIST PROCESSING MANUAL
This is a manual method of adding all array’s elements to List. We can use this method if we don’t want to use java in built method (s). If you check the console log, you will notice that exception is thrown by Iterator next() method. Method 3: Using Manual method to convert Array using add () method. What it means is that once the iterator is created, if the ArrayList is modified, it throws ConcurrentModificationException. Illustration: Input: 2, 3, 4, 2, 7 Processing : index 4. we noticed array copy operation taking a significant amount of processing time. Being a good programmer one is already aware of using ArrayList over arrays despite knowing the differences between these two. ArrayList is the Resizable-array implementation of the List interface. It happens because ArrayList iterator is fail-fast by design. Method 1: Swap two elements using get and set methods of ArrayList: In this method. As we all are aware of that arrays are linear data structures providing functionality to add elements in a continuous manner in memory address space whereas ArrayList is a class belonging to the Collection framework. When we run above program, we get as soon as the ArrayList is modified. Arrays are fixed size ArrayList's size auotomatically adjusted Arrays can hold primitives and object ArrayList can hold only objects Arrays can be multi dimensional ArrayList cannot be multi-dimentional Array is a build in data structure ArrayList is. because it doesn't change modCount variable of list The point is that data and processing are handled as a unit.
ARRAY VS ARRAYLIST PROCESSING CODE
below code don't throw ConcurrentModificationException Class Data (variable) Processing (method / function). Let’s check a sample program of ArrayList.
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