Collections_Generics_ExceptionHandling

Why are ArrayLists better than arrays ?

• • You don't have to decide the size of an ArrayList when you first make it.

• • You can put more items into an ArrayList than into an array.

• • ArrayLists can hold more kinds of objects than arrays.

• • You don't have to decide the type of an ArrayList when you first make it.

You get a NullPointerException. What is the most likely cause?

• A file that needs to be opened cannot be found.

• • A network connection has been lost in the middle of communications.

• • Your code has used up all available memory.

• • The object you are using has not been instantiated.

What is the output of this code?

• [abc, 0, 2, 10]

• The code does not compile.

• • [abc, 2, 10, 0]

• [0, 10, 2, abc]

Which code snippet is valid ?

• • ArrayList<String> words = new ArrayList<String>(){"Hello", "World"};

• • ArrayList words = Arrays.asList("Hello", "World");

• • ArrayList<String> words = new ArrayList<>(Arrays.asList("Hello", "World"));

• • ArrayList<String> words = {"Hello", "World"};

Which characteristic does not apply to instances of java.util.HashSet?

• • uses hashcode of objects when inserted

• • contains unordred elements

• • contains unique elements

• • contains sorted elements

You have an instance of type Map<String, Integer> named instruments containing the following key-value pairs: guitar=1200, cello=3000, and drum=2000. If you add the new key-value pair cello=4500 to the Map using the put method, how many elements do you have in the Map when you call instruments.size()?

• 2

• 3

• 4

• • When calling the put method, Java will throw an exception

What is the result of this code?

• • Hello World

• • It will not compile because the second catch statement is unreachable

• Hello World!

• It will throw a runtime exception

Which class acts as the root class for the Java Exception hierarchy?

• Clonable

• Throwable

• Object

• Serializable

Which class does not implement the java.util.Collection interface ?

• • java.util.Vector

• java.util.ArrayList

• java.util.HashSet

• • java.util.HashMap

Which language feature ensures that objects implementing the AutoCloseable interface are closed when it completes?

• try-catch-finally

• try-finally-close

• try-with-resources

• try-catch-close