.

Also know, how do you compare two values on a map?

The correct way to compare maps for value-equality is to:

1. Check that the maps are the same size(!)
2. Get the set of keys from one map.
3. For each key from that set you retrieved, check that the value retrieved from each map for that key is the same (if the key is absent from one map, that's a total failure of equality)

Beside above, what is entrySet and keySet in Java? The java.util.Map interface provides three methods keySet(), values() and entrySet(), which allow a map's contents to be viewed as a set of keys, collection of values, or set of key-value mappings respectively.

Keeping this in consideration, how do you compare two Arraylists?

You can compare two array lists using the equals() method of the ArrayList class, this method accepts a list object as a parameter, compares it with the current object, in case of the match it returns true and if not it returns false.

What is HashMap in Java?

HashMap is a part of Java's collection since Java 1.2. It provides the basic implementation of the Map interface of Java. It stores the data in (Key, Value) pairs. To access a value one must know its key. HashMap is known as HashMap because it uses a technique called Hashing.