Servlet interview questions and answers for experienced pdf

What is immutable object in Java? Can you change values of a immutable object? A Java object is considered immutable when its state cannot change after it is created. Use of immutable objects is widely accepted as a sound servlet interview questions and answers for experienced pdf for creating simple, reliable code.

Immutable objects are particularly useful in concurrent applications. Since they cannot change state, they cannot be corrupted by thread interference or observed in an inconsistent state. Integer classes are the Examples of immutable objects from the Java Development Kit. Immutable objects are simple to use test and construct. Immutable objects are automatically thread-safe. Immutable objects do not require a copy constructor. Immutable objects do not require an implementation of clone.

Immutable objects do not need to be copied defensively when used as a field. Immutable objects have their class invariant established once upon construction, and it never needs to be checked again. How to create a immutable object in Java? Does all property of immutable object needs to be final? To create a object immutable You need to make the class final and all its member final so that once objects gets crated no one can modify its state. You can achieve same functionality by making member as non final but private and not modifying them except in constructor.

Also its NOT necessary to have all the properties final since you can achieve same functionality by making member as non final but private and not modifying them except in constructor. The main difference between the three most commonly used String classes as follows. If the Object value will not change in a scenario use String Class because a String object is immutable. Why String class is final or immutable? It is very useful to have strings implemented as final or immutable objects. Two threads can both work on an immutable object at the same time without any possibility of conflict. You can share duplicates by pointing them to a single instance.

You can create substrings without copying. You just create a pointer into an existing base String guaranteed never to change. Immutability is the secret that makes Java substring implementation very fast. Immutable objects are good fit for becoming Hashtable keys. If you change the value of any object that is used as a hash table key without removing it and re-adding it you will lose the object mapping. Since String is immutable, inside each String is a char exactly the correct length.