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Try-Catch-blokken
In Java, runtime errors are handled using Exceptions. Exception handling allows us to intercept anomalous conditions and prevent the program from crashing.
The try-catch structure
To handle a potential exception, we enclose the risky code in a try block. If an error occurs inside the try block, the JVM stops executing it and searches for a matching catch block to handle the exception.
try {
int result = 10 / 0; // Generates ArithmeticException
System.out.println("This will not be printed");
} catch (ArithmeticException e) {
System.out.println("Arithmetic error occurred: " + e.getMessage());
}
The finally block
The finally block is optional and is always executed, regardless of whether an exception was thrown. It is ideal for releasing resources or performing cleanup operations.
try {
System.out.println("Executing logic");
} catch (Exception e) {
System.out.println("Error");
} finally {
System.out.println("This block is always executed");
}
Throwing Exceptions: throw
We can intentionally throw an exception using the throw keyword followed by a new instance of an exception class.
public static void checkScore(int score) {
if (score < 0 || score > 100) {
throw new IllegalArgumentException("Score must be between 0 and 100");
}
}
Try it yourself
Complete the code by inserting a try-catch block to handle a potential ArithmeticException resulting from the division a / b. In case of an error, print 'Error: division by zero'.
Toon hint
Insert the division operation inside a `try` block and catch `ArithmeticException`, printing the required message.
Oplossing beschikbaar na 3 pogingen
Complete the code to implement a try-catch-finally block. In the try block, try to convert the string str to an integer using Integer.parseInt. In the catch block, intercept NumberFormatException and print 'Invalid number'. In the finally block, print 'Finally'.
Toon hint
Write the `try { ... } catch (NumberFormatException e) { ... } finally { ... }` block structure.
Oplossing beschikbaar na 3 pogingen
Complete the checkAge method by throwing an IllegalArgumentException with the message 'Underage' if the provided age is less than 18.
Toon hint
Use `if (age < 18)` and the `throw new` keywords to instantiate and throw the exception.
Oplossing beschikbaar na 3 pogingen