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Question 1

A person says that he compiled a java class successfully without even having a main method in it? Is it possible?

Answer 1

main method is an entry point of Java class and is required for execution of the program however; a class gets compiled successfully even if it doesn’t have a main method. It can’t be run though.

Question 2

Can we call a non-static method from inside a static method?

Answer 2

Non-Static methods are owned by objects of a class and have object level scope and in order to call the non-Static methods from a static block (like from a static main method), an object of the class needs to be created first. Then using object reference, these methods can be invoked.

Question 3

What are the two environment variables that must be set in order to run any Java programs?

Answer 3

Java programs can be executed in a machine only once following two environment variables have been properly set:

PATH variable
CLASSPATH variable

Question 4

Can variables be used in Java without initialization?

Answer 4

In Java, if a variable is used in a code without prior initialization by a valid value, program doesn’t compile and gives an error as no default value is assigned to variables in Java.

Question 5

Can a class in Java be inherited from more than one class?

Answer 5

In Java, a class can be derived from only one class and not from multiple classes. Multiple inheritances is not supported by Java.

Question 6

Can a constructor have different name than a Class name in Java?

Answer 6

Constructor in Java must have same name as the class name and if the name is different, it doesn’t act as a constructor and compiler thinks of it as a normal method.

Question 7

Can a dead thread be started again?

Answer 7

In java, a thread which is in dead state can’t be started again. There is no way to restart a dead thread.