Java Questions

There are lots of ways to solve the issue of callback hells:

1. Modularization: break callbacks into independent functions
2. Use a control flow library, like async
3. Use generators with Promises
4. Use async/await (note that it is only available in the latest v7 release and not in the LTS version)

To make this method available to every implementation class

Overloading allows multiple functions to exist with same name but different parameters. Again if you take bike as an example, it has a function “Start” with two forms i.e. ’Auto Start’ and ’kick start’.

A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

Executing two or more blocks (threads) of a program at a time is called MultiThreading.

Java Collections Framework provides a well designed set of interfaces and classes that support operations on a collections of objects. The most basic interfaces that reside in the Java Collections Framework are:

Collection, which represents a group of objects known as its elements.

Set, which is a collection that cannot contain duplicate elements.

List, which is an ordered collection and can contain duplicate elements.

Map, which is an object that maps keys to values and cannot contain duplicate keys.

A static variable in Java belongs to its class and its value remains the same for all its instances. A static variable is initialized when the class is loaded by the JVM. If your code tries to access a non-static variable, without any instance, the compiler will complain, because those variables are not created yet and they are not associated with any instance.