Java Basics Quiz

Question 1

Which of the following is not a Java keyword?

Accepted Answer

'main' is not a keyword in Java. It is a method name. Keywords like 'static', 'boolean', and 'void' are reserved words with special meaning in Java.

Question 2

What is the default value of a boolean variable in Java?

Accepted Answer

The default value of a boolean instance variable is false. For local variables, there is no default value and must be initialized before use.

Question 3

Which method must be implemented by all threads in Java?

Accepted Answer

The run() method must be implemented when creating a thread by extending Thread class or implementing Runnable interface. It contains the code to be executed by the thread.

Question 4

What is the range of byte data type in Java?

Accepted Answer

The byte data type is an 8-bit signed two's complement integer with a minimum value of -128 and a maximum value of 127 (inclusive).

Question 5

Which of these access modifiers can be used for an interface?

Accepted Answer

An interface can only be declared as public or package-private (default). Protected and private access modifiers cannot be used for top-level interfaces.

Question 6

What will be the output of: System.out.println(10 + 20 + "Java" + 30 + 40);

Accepted Answer

In Java, the + operator is evaluated left to right. First 10+20=30, then 30 is concatenated with 'Java' giving '30Java', then '30Java30' and finally '30Java3040'.

Question 7

Which exception is thrown when an array is accessed with an invalid index?

Accepted Answer

ArrayIndexOutOfBoundsException is thrown when trying to access an array with an illegal index (negative or greater than or equal to the array size).

Question 8

Can we override static methods in Java?

Accepted Answer

Static methods cannot be overridden. They belong to the class, not to instances. If a subclass defines a static method with the same signature, it's called method hiding, not overriding.