OCP Exception Handling and Assertions Questions and Answers

Question 1

Examine the following code which uses a try-with-resources statement. What is the output when this code is executed?

```java
class Door implements AutoCloseable {
    private String name;
    public Door(String name) { this.name = name; System.out.println(name + " opened"); }
    @Override
    public void close() { System.out.println(name + " closed"); }
}

public class Test {
    public static void main(String[] args) {
        try (Door front = new Door("Front"); Door back = new Door("Back")) {
            System.out.println("Walking through doors");
        } 
    }
}
```

Accepted Answer

Front opened
Back opened
Walking through doors
Back closed
Front closed

Answer

Front opened
Back opened
Walking through doors
Front closed
Back closed

Answer

Front opened
Walking through doors
Front closed
Back opened
Back closed

Answer

The code will not compile because multiple resources are declared.

Question 2

What is the final value returned by the `checkValue` method when executed?

```java
public class Test {
    public static int checkValue() {
        try {
            System.out.println("Executing try");
            return 10;
        } catch (Exception e) {
            System.out.println("Executing catch");
            return 20;
        } finally {
            System.out.println("Executing finally");
            return 30;
        }
    }

public static void main(String[] args) {
        System.out.println("Returned: " + checkValue());
    }
}
```

Accepted Answer

30

Answer

20

Answer

10

Answer

The code will not compile because a `finally` block cannot have a `return` statement.

Question 3

Which of the following statements about the `assert` keyword in Java is true?

Accepted Answer

Assertions can be enabled at runtime using the `-ea` flag and are primarily intended for debugging and testing.

Answer

Assertions are a replacement for standard exception handling for public methods.

Answer

An `AssertionError` is a checked exception that must be caught or declared.

Answer

Assertions are enabled by default and must be disabled with the `-da` flag.

Question 4

A method is declared to throw both `java.io.IOException` and `java.sql.SQLException`. Which of the following `catch` clauses is the correct and most concise way to handle both of these distinct exception types in a single block?

Accepted Answer

```java
catch (IOException | SQLException e) { /* ... */ } 
```

Answer

```java
catch (IOException e1, SQLException e2) { /* ... */ } 
```

Answer

```java
catch (Exception e) { /* ... */ } 
```

Answer

```java
catch (IOException & SQLException e) { /* ... */ } 
```

Question 5

Which of the following exceptions is a checked exception that the Java compiler requires to be handled or declared?

Accepted Answer

java.io.FileNotFoundException

Answer

NullPointerException

Answer

ArrayIndexOutOfBoundsException

Answer

ClassCastException

Question 6

Consider a `try-with-resources` statement. If an exception is thrown within the `try` block, and a different exception is thrown when the resource's `close()` method is automatically called, what happens?

Accepted Answer

The exception from the `try` block is thrown, and the exception from the `close()` method is added to it as a suppressed exception.

Answer

Only the exception from the `close()` method is thrown, as it occurs last.

Answer

The program terminates immediately without throwing any specific exception.

Answer

Both exceptions are thrown, and the calling method must have two separate `catch` blocks to handle them.