Throws keyword in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the throws keyword in Java?

The throws keyword is used in a method signature to declare that the method might throw certain checked exceptions. It tells the caller to handle or further declare these exceptions.

beginner

How does throws differ from throw in Java?

throw is used to actually throw an exception object inside a method, while throws declares that a method might throw exceptions, informing the caller to handle them.

intermediate

Can a method declare multiple exceptions with throws? How?

Yes, a method can declare multiple exceptions by listing them separated by commas after the throws keyword, for example: void myMethod() throws IOException, SQLException.

beginner

What happens if a method does not handle a checked exception and does not declare it with throws?

The Java compiler will produce an error because checked exceptions must be either caught with a try-catch block or declared with throws in the method signature.

intermediate

Is it mandatory to declare unchecked exceptions with throws?

No, unchecked exceptions (like RuntimeException) do not need to be declared with throws. It is optional because they can occur anywhere and are not checked at compile time.

What does the throws keyword do in a Java method?

A Creates a new exception object

B Declares exceptions that the method might throw

C Catches exceptions inside the method

D Prevents exceptions from occurring

The throws keyword declares exceptions that the method might throw, informing callers to handle them.

Which of these is a correct way to declare multiple exceptions using throws?

A void example() throws IOException, SQLException

B void example() throws IOException SQLException

C void example() throw IOException, SQLException

D void example() throws (IOException, SQLException)

Multiple exceptions are declared separated by commas after the throws keyword without parentheses.

If a method throws a checked exception but does not declare it with throws, what happens?

A The exception is ignored at runtime

B The program compiles and runs fine

C The compiler gives an error

D The method automatically catches the exception

The compiler requires checked exceptions to be declared or caught; otherwise, it produces an error.

Which keyword is used to actually throw an exception object inside a method?

A throw

B throws

C catch

D try

throw is used to throw an exception object, while throws declares exceptions.

Is it necessary to declare unchecked exceptions with throws?

A Only if the method catches them

B No, never

C Yes, always

D Optional, but usually not declared

Unchecked exceptions do not have to be declared with throws, but it is allowed.

Explain the role of the throws keyword in Java methods and how it helps with exception handling.

Think about how Java forces you to handle certain errors.

Describe the difference between throw and throws keywords in Java with examples.

One is for declaring, the other is for actually throwing.