CH11 - Exceptions and Localization

Question 1

Unchecked Exception

Answer 1

An unchecked exception is any exception that does not need to be declared or handled by the application code it is thrown.

Unchecked exceptions are often referred to as runtime exceptions.

Question 2

Error

Answer 2

Error means something went so horribly wrong that your program should not attempt to recover from it.

Question 3

Throwable

Answer 3

Throwable is that it’s the parent class of all exceptions, including the Error class.

While you can handle Throwable and Error exceptions, it is not recommended you do so in your app code.

Question 4

Checked Exception

Answer 4

Subclass of Exception but not subclass of RuntimeException

Question 5

Unchecked Exception

Answer 5

Subclass of RuntimeException

Question 6

Overriding method with Exception

Answer 6

An overridden method may not declare any new or broader checked exceptions that the method it inherits.

An overridden method in a subclass is allowed to declare fewer exceptions than the superclass or interface.

Question 7

try-with-resources

Answer 7

Only classes that implement the AutoCloseable interface can be used in a try-with-resources statement.

Inheriting AutoClosable requires implementing a compatible close() method

Question 8

Closable

Answer 8

Closeable extends AutoClosable they are both supported in try-with-resources statements.

Difference Closeable’s close() method declares IOException, while AutoCloseable’s close() method declares Exception.

Question 9

Scope of Try-With-Resources

Answer 9

The resources created in the try clause are in scope only within the try block.

This is anoter way to remember that the implicit finally runs before any catch/finally blocks that you code yourself.

Question 10

📦 NumberFormat — What It Does

Answer 10

-Formats numbers as plain numbers, currency, or percentages

-Parses strings back into numbers

-Adapts to locales (e.g., decimal separator in US vs Germany)

Question 11

Common Subclasses of NumberFormat

Answer 11

NumberFormat
DecimalFormat
Currency
Percent

Question 12

Basic Number Formatting

Answer 12

NumberFormat nf = NumberFormat.getInstance();

System.out.println(nf.format(1234567.89)); // e.g., “1,234,567.89” (in US)

Question 13

Locale-Specific Formatting

Answer 13

NumberFormat nfFR = NumberFormat.getInstance(Locale.FRANCE);
System.out.println(nfFR.format(1234567.89));

// e.g., “1234567,89”

Question 14

📌 Rules for Custom Text:

Answer 14

Wrap any literal text in single quotes ‘…’.

To write a single quote character, use ‘’ (double single quote).

DateTimeFormatter formatter = DateTimeFormatter.ofPattern(“hh:mm a ‘o’‘clock’”);
// Output: 03:25 PM o’clock

Question 15

Unchecked exceptions can be thrown in any method,
Is it coorect claim?

Answer 15

YES

In Java, unchecked exceptions (also called runtime exceptions) are:

Subclasses of RuntimeException

Not required to be declared in a method’s throws clause

Can be thrown in any method, at any time

Question 16

Multi-catch block

Answer 16

In multi-catch block, all caught exception types must be disjoint - i.e. no subtype - supertype relationships.
Otherwise, one of the exception types would never be reached.

In a multi-catch block, all exception types must be unrelated(disjoint) - no subtype/supertype relationship - to avoid unreachable code.

Question 17

try-with-resources

Answer 17

It must be either:
-Declared inside the try block
- Effectively final (nor reassigned after initialized)