A NullPointerException is a runtime exception in Java that happens when you attempt to perform an operation on a null object reference. In other words, you're attempting to access a member (such as a method or field) of an object that hasn't yet been initialized, which results in a null reference.
The java.lang.IndexOutOfBoundsException is an exception class in Java that is thrown when an index used to access an array, list, or other collection is either negative or greater than or equal to the size of the collection. This usually indicates an attempt to access an element at an invalid index that does not exist in the collection.
The Treemap is a component of the Java Collections Framework that implements the SortedMap interface. It keeps its elements ordered according to the natural ordering of keys or a defined comparator.
A dynamic array implementation that is a part of the Java Collections Framework is the Vector class in Java. It offers a resizable array that can expand or contract as necessary. Similar to ArrayLists, vectors are thread-safe for use in multi-threaded situations since they are synchronised.