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The WatchKey take() method retrieves and removes next watch key, waiting if none are yet present.Note: A watch service that watches registered objects for changes and events. For example a file manager may use a watch service to monitor a directory for changes so that it can update its display of the list of files when files are created or deleted.A Watchable object is registered with a watch service by invoking its register method, returning a WatchKey to represent the registration. When an event for an object is detected the key is signalled, and if not currently signalled, it is queued to the watch service so that it can be retrieved by consumers that invoke the poll or take methods to retrieve keys and process events. Once the events have been processed the consumer invokes the key's reset method to reset the key which allows the key to be signalled and re-queued with further events.Reference: Interface WatchService

B: Two mutually exclusive exceptions. Will work fine.D: A single exception. Will work fine.E: Two mutually exclusive exceptions. Will work fine.Note: In Java SE 7 and later, a single catch block can handle more than one type of exception. This feature can reduce code duplication and lessen the temptation to catch an overly broad exception.In the catch clause, specify the types of exceptions that block can handle, and separate each exception type with a vertical bar (|).Note 2: NoSuchFileException: Checked exception thrown when an attempt is made to access a file that does not exist.InvalidPathException: Unchecked exception thrown when path string cannot be converted into a Path because the path string contains invalid characters, or the path string is invalid for other file system specific reasons.FileNotFoundException: Signals that an attempt to open the file denoted by a specified pathname has failed.This exception will be thrown by the FileInputStream, FileOutputStream, andRandomAccessFile constructors when a file with the specified pathname does not exist. It will also be thrown by these constructors if the file does exist but for some reason is inaccessible, for example when an attempt is made to open a read-only file for writing.

C: The method walkFileTree(Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor) walks a file tree.The maxDepth parameter is the maximum number of levels of directories to visit. A value of0 means that only the starting file is visited, unless denied by the security manager. A value of MAX_VALUE may be used to indicate that all levels should be visited. The visitFile method is invoked for all files, including directories, encountered at maxDepth, unless the basic file attributes cannot be read, in which case the visitFileFailed method is invoked.D: You need to decide whether you want symbolic links to be followed. If you are deleting files, for example, following symbolic links might not be advisable. If you are copying a file tree, you might want to allow it. By default, walkFileTree does not follow symbolic links.Reference: The Java Tutorials, Walking the File TreeReference: walkFileTree -

Note: You can replace the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (<>) as long as the compiler can infer the type arguments from the context. This pair of angle brackets is informally called the diamond.

DriverManager has a factory method getConnection() that returns aConnection object.Note 1: A factory method is a method that creates and returns new objects.The factory pattern (also known as the factory method pattern) is a creational design pattern. A factory is a Java class that is used to encapsulate object creation code. A factory class instantiates and returns a particular type of object based on data passed to the factory. The different types of objects that are returned from a factory typically are subclasses of a common parent class.Note 2:The method DriverManager.getConnection establishes a database connection. This method requires a database URL, which varies depending on your DBMS. The following are some examples of database URLs: MySQL, Java DB.

DateFormat is an abstract class that provides the ability to format and parse dates and times. The getDateInstance() method returns an instance of DateFormat that can format date information. It is available in these forms: static final DateFormat getDateInstance( ) static final DateFormat getDateInstance(int style) static final DateFormat getDateInstance(int style, Locale locale)The argument style is one of the following values: DEFAULT, SHORT, MEDIUM, LONG, orFULL. These are int constants defined by DateFormat.

Compiles fine, but runtime error when trying to access the Spanish Resource bundle (which does not exist):Exception in thread "main" java.util.MissingResourceException: Can't find bundle for base name messageBundle, locale es_ES

A set is a collection that contains no duplicate elements. So set will include only two elements at the start of while loop. The while loop will execute once for each element. Each element will be printed.Note:* public interface IteratorAn iterator over a collection. Iterator takes the place of Enumeration in the Java collections framework. Iterators differ from enumerations in two ways:Iterators allow the caller to remove elements from the underlying collection during the iteration with well-defined semantics.Method names have been improved.* hasNextpublic boolean hasNext()Returns true if the iteration has more elements. (In other words, returns true if next would return an element rather than throwing an exception.)* nextpublic Object next()Returns the next element in the iteration.

CopyOnWriteArrayList produces a thread-safe variant of ArrayList in which all mutative operations (add, set, and so on) are implemented by making a fresh copy of the underlying array.Note: his is ordinarily too costly, but may be more efficient than alternatives when traversal operations vastly outnumber mutations, and is useful when you cannot or don't want to synchronize traversals, yet need to preclude interference among concurrent threads. The "snapshot" style iterator method uses a reference to the state of the array at the point that the iterator was created. This array never changes during the lifetime of the iterator, so interference is impossible and the iterator is guaranteed not to throw ConcurrentModificationException. The iterator will not reflect additions, removals, or changes to the list since the iterator was created. Element-changing operations on iterators themselves (remove, set, and add) are not supported. These methods throw UnsupportedOperationException.All elements are permitted, including null.Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a CopyOnWriteArrayList happen-before actions subsequent to the access or removal of that element from the CopyOnWriteArrayList in another thread.Reference: java.util.concurrent.CopyOnWriteArrayList<E>