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

Which could be used to create an appropriate catch block?

When creating a thread by extending the Thread class, it is not mandatory to override the run method (If we are not overriding the run method , it is useless), because Thread class have already given a default implementation for run method. But if we are implementing Runnable , it is mandatory to override the run method. The preferred way to create a thread is by implementing Runnable interface, because it give loose coupling.

A thread can be created by subclassing Thread, or by implementing the Runnable interface.

When an exception is thrown , the catch block of the try statement are examined in the order in which they appear. The first catch block that is capable of handling the exception is executed. The remaining catch blocks are ignored

A static initializer block is a block of code that declares with the static keyword. It normally contains the block of code that must execute at the time of class loading. The static initializer block will execute only once at the time of loading the class only.

Overridden methods must have the same name, argument list, and return type (i.e., they must have the exact signature of the method we are going to override, including return type.)

The overriding method cannot be less visible than the method it overrides( i.e., a public method cannot be override to private).

The overriding method may not throw any exceptions that may not be thrown by the overridden method

Yes, we can. In order to compile a java program, we don't require any main method. But to execute a java program we must have a main in it (unless it is an applet or servlet). Because main is the starting point of a java program.

Inheritance is the ability to create new classes based on existing classes. It is useful to reuse existing code.

Encapsulation describes the ability of an object to hide its data and methods from the rest of the world