try { int x = Integer.parseInt("two"); }

Which could be used to create an appropriate catch block?

Overriding is a method with the same name and arguments as in a parent, whereas overloading is the same method name but different arguments

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.

These are accessibility modifiers. Private is the most restrictive, while public is the least restrictive. There is no real difference between protected and the default type (also known as package protected) within the context of the same package, however the protected keyword allows visibility to a derived class in a different package.

You should declared your class as final. But you can't define your class as final, if it is an abstract class. A class declared as final can't be extended by any other class.

A method declared as final can't be overridden. A sub-class can't have the same method signature with a different implementation.

Package is a collection of related classes and interfaces. package declaration should be first statement in a java class.

Path and Classpath are operating system level environment variales. Path is used define where the system can find the executables(.exe) files and classpath is used to specify the location .class files.

A thread is a lightweight subprocess, a smallest unit of processing. It is a separate path of execution. It shares the memory area of process.

As shown in the above figure, thread is executed inside the process. There is context-switching between the threads. There can be multiple processes inside the OS and one process can have multiple threads.