1Z0-819 Exception Handling & Concurrency

Question 1

What is the purpose of exception handling in Java?

Accepted Answer

To handle errors gracefully during runtime

Answer

Exception handling in Java provides a structured way to deal with runtime errors, known as exceptions, that disrupt the normal flow of program execution. Its primary purpose is to prevent programs from crashing abruptly and instead allow them to recover gracefully or terminate in a controlled manner, improving robustness. It does not aim to stop execution immediately, increase complexity, or reduce performance, but rather to manage unexpected situations effectively.

Question 2

Which block must always follow a try block?

Accepted Answer

finally

Answer

In Java's exception handling mechanism, a `try` block must always be followed by either a `catch` block, a `finally` block, or both. The `finally` block is crucial because the code within it is guaranteed to execute, regardless of whether an exception was thrown or caught in the `try` block. This makes it ideal for cleanup operations like closing resources.

Question 3

What is a checked exception in Java?

Accepted Answer

Exceptions that must be declared or handled

Answer

A checked exception in Java is an exception that the compiler enforces you to handle. This means that methods throwing checked exceptions must either declare them using the `throws` keyword in their signature or enclose the problematic code within a `try-catch` block. This design ensures that developers explicitly consider and address potential error conditions, making programs more robust.

Question 4

Which class is the superclass of all exceptions?

Accepted Answer

Throwable

Answer

In Java's exception hierarchy, `java.lang.Throwable` is the root class for all exceptions and errors. Both `java.lang.Exception` and `java.lang.Error` are direct subclasses of `Throwable`. Therefore, any object that can be thrown by the `throw` statement must be an instance of `Throwable` or one of its subclasses.

Question 5

How is a thread created in Java?

Accepted Answer

By extending Thread or implementing Runnable

Answer

In Java, there are two primary ways to create a thread: by extending the `java.lang.Thread` class or by implementing the `java.lang.Runnable` interface. Both approaches require defining the code to be executed by the thread within a `run()` method. Extending `Thread` is simpler for single-use cases, while implementing `Runnable` is preferred for better code organization and when the class already extends another class.

(1Z0-819) Oracle Java SE 11 Developer Practice Test

(1Z0-819) Oracle Java SE 11 Developer Practice Test

1Z0-819 Exception Handling & Concurrency