Oracle 1Z0-805 Online Practice Questions and Exam Preparation

Oracle 1Z0-805 Online Questions & Answers

• Question 81:

  Given this code fragment:

  ResultSet rs = null;

  try (Connection conn = DriverManager. getConnection (url) )

  { Statement stmt = conn.createStatement();

  rs stmt.executeQuery(query);

  //-.. other methods }

  } catch (SQLException se)

  { System.out.println ("Error");

  }

  Which object is valid after the try block runs?

  A. The Connection object only
  B. The Statement object only
  C. The Result set object only
  D. The Statement and Result Set object only
  E. The connection, statement, and ResultSet objects
  F. Neither the Connection, Statement, nor ResultSet objects
  C. The Result set object only

  ---

  Generally, JavaScript has just 2 levels of scope: global and function. But, try/catch is an exception (no punn intended). When an exception is thrown and the exception object gets a variable assigned to it, that object variable is only available within the "catch" section and is destroyed as soon as the catch completes.

• Question 82:

  Which two file attribute views support reading or updating the owner of a file?

  A. AclFileAttributeView
  B. DosFileAttributeView
  C. FileOwnerAttributeView
  D. FileStoreAttributeView
  E. BasicFileAttributeView
  A. AclFileAttributeView
  C. FileOwnerAttributeView

  ---

  A: The AclFileAttributeView is a file attribute view that supports reading or updating a file's Access Control Lists (ACL) or file owner attributes.

  C: The FileOwnerAttributeView.setOwner(UserPrincipal owner) method updates the file owner. Reference:Interface AclFileAttributeView,Interface FileOwnerAttributeView

• Question 83:

  Which two descriptions are benefits of using PreparedStatement objects over static SQL in JDBC?

  A. Conversion to native SQL
  B. Supports BLOB types on every type of database
  C. Prevention of SQL injection attacks
  D. Improved performance from frequently run SQL queries
  E. Built in support for multi database transaction semantics
  A. Conversion to native SQL
  D. Improved performance from frequently run SQL queries

  ---

  Sometimes it is more convenient to use a PreparedStatement object for sending SQL statements to the database. This special type of statement is derived from the more general class, Statement, that you already know.

  If you want to execute a Statement object many times, it usually reduces execution time to use a PreparedStatement object instead.

  The main feature of a PreparedStatement object is that, unlike a Statement object, it is given a SQL statement when it is created. The advantage to this is that in most cases, this SQL statement is sent to the DBMS right away, where it is

  compiled. As a result, the PreparedStatement object contains not just a SQL statement, but a SQL statement that has been precompiled. This means that when the PreparedStatement is executed, the DBMS can just run the

  PreparedStatement SQL statement without having to compile it first.

  Although PreparedStatement objects can be used for SQL statements with no parameters, you probably use them most often for SQL statements that take parameters. The advantage of using SQL statements that take parameters is that you

  can use the same statement and supply it with different values each time you execute it.

  Reference: The Java Tutorials, Using Prepared Statements

• Question 84:

  Which method or methods should you implement to create your own implementation of the java.nio.file.PathMatcher interface?

  A. matches(Path)
  B. matches(Path), fails(Path)
  C. matches(Path) , fails(Path), enable(boolean)
  D. matches(Path) , fails(Path) , setPreferred (String)
  A. matches(Path)

  ---

  The interface PathMatcher is an interface that is implemented by objects that perform match operations on paths.

  The single method for this interface ismatches:

  boolean matches(Path path)

  Tells if given path matches this matcher's pattern.

  Parameters:

  path - the path to match

  Returns:

  true if, and only if, the path matches this matcher's pattern.

  Reference: java.nio.file.PathMatcher

• Question 85:

  Given the code fragment:

  SimpleDateFormat sdf;

  Which code fragment displays the three-character month abbreviation?

  A. sdf = new SimpleDateFormat ("mm", Locale.UK); System.out.println ("Result:"+ sdf.format(new Date()));
  B. sdf = new SimpleDateFormat ("MM", Locale.UK); System.out.println ("Result:"+ sdf.format(new Date()));
  C. sdf = new SimpleDateFormat ("MMM", Locale.UK); System.out.println ("Result:"+ sdf.format(new Date()));
  D. sdf = new SimpleDateFormat ("MMMM", Locale.UK); System.out.println ("Result:"+ sdf.format(new Date()));
  C. sdf = new SimpleDateFormat ("MMM", Locale.UK); System.out.println ("Result:"+ sdf.format(new Date()));

  ---

  C: Output example: Apr

  Note:SimpleDateFormat is a concrete class for formatting and parsing dates in a locale-sensitive manner. It allows for formatting (date -> text), parsing (text -> date), and normalization. SimpleDateFormat allows you to start by choosing any user-defined patterns for date-time formatting. However, you are encouraged to create a date-time formatter with either getTimeInstance, getDateInstance, orgetDateTimeInstance in DateFormat. Each of these class methods can return a date/time formatter initialized with a default format pattern. You may modify the format pattern using the applyPattern methods as desired.

• Question 86:

  Given:

  class Fibonacci extends RecursiveTask {

  final int n;

  Fibonacci (int n) { this.n = n }

  Integer compute () {

  if (n <= 1)

  return n;

  Fibonacci f1 = new Fibonacci (n ?1);

  f1.fork;

  Fibonacci f2 = new Fibonacci (n ?2);

  return f2.compute() + f1.join; // Line **

  }

  }

  Assume that line ** is replaced with:

  return f1.join() + f2.compute(); // Line **

  What is the likely result?

  A. The program produces the correct result, with similar performance to the original.
  B. The program produces the correct result, with performance degraded to the equivalent of being single-threaded.
  C. The program produces an incorrect result.
  D. The program goes into an infinite loop.
  E. An exception is thrown at runtime.
  F. The program produces the correct result, with better performance than the original.
  B. The program produces the correct result, with performance degraded to the equivalent of being single-threaded.

  ---

  Changing the code is not useful. In the original code (return f2.compute() + f1.join; ) f1 and f2 are run in parallel. The result is joined. With the changed code (return f1.join() + f2.compute();) f1 is first executed and finished, then is f2 executed.

  Note 1:The join method allows one thread to wait for the completion of another. If t is a Thread object whose thread is currently executing, t.join(); causes the current thread to pause execution until t's thread terminates.

  Note 2:New in the Java SE 7 release, the fork/join framework is an implementation of the ExecutorService interface that helps you take advantage of multiple processors. It is designed for work that can be broken into smaller pieces recursively. The goal is to use all the available processing power to enhance the performance of your application.

  As with any ExecutorService, the fork/join framework distributes tasks to worker threads in a thread pool. The fork/join framework is distinct because it uses a work-stealing algorithm. Worker threads that run out of things to do can steal tasks from other threads that are still busy.

  Reference: The Java Tutorials,Joins,Fork/Join

• Question 87:

  Given:

  

  What two changes should you make to apply the DAO pattern to this class?

  A. Make the customer class abstract.
  B. Make the customer class an interface.
  C. Move the add, delete, find, and update methods into their own implementation class.
  D. Create an interface that defines the signatures of the add, delete, find and update command.
  E. Make the add, delete, find, and update methods private for encapsulation.
  F. Make the getName and getId methods private fir encapsulation.
  C. Move the add, delete, find, and update methods into their own implementation class.
  D. Create an interface that defines the signatures of the add, delete, find and update command.

  ---

  In computer software, a data access object (DAO) is an object that provides an abstract interface to some type of database or persistence mechanism, providing some specific operations without exposing details of the database. It provides a mapping from application calls to the persistence layer. This isolation separates the concerns of what data accesses the application needs, in terms of domain-specific objects and data types (the public interface of the DAO), and how these needs can be satisfied with a specific DBMS, database schema, etc. (the implementation of the DAO).

  In the specific context of the Java programming language, Data Access Objects as a design concept can be implemented in a number of ways. This can range from a fairly simple interface that separates the data access parts from the application logic, to frameworks and commercial products.

• Question 88:

  Which statement is true about the take method defined in the WatchService interface?

  A. Retrieves and removes the next watch key, or returns null of none are present.
  B. Retrieves and removes the next watch key. If a queued key is not immediately available, the program waits for the specified wait time.
  C. Retrieves and removes the next watch key: waits if no key is yet present.
  D. Retrieves and removes all pending events for the watch key, returning a list of the events that were retrieved.
  C. Retrieves and removes the next watch key: waits if no key is yet present.

  ---

  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

• Question 89:

  Which three enum constants are defined in FilevisitResult?

  A. CONTINUE
  B. SKIP_SIBLINGS
  C. FOLLOW_LINKS
  D. TERMINATE
  E. NOFOLLOW_LINKS
  F. DELETE_CHILD
  A. CONTINUE
  B. SKIP_SIBLINGS
  D. TERMINATE

  ---

  The FileVisitor methods return a FileVisitResult value. You can abort the file walking process or control whether a directory is visited by the values you return in the FileVisitor methods:

  *

  CONTINUE ?Indicates that the file walking should continue. If the preVisitDirectory method returns CONTINUE, the directory is visited.

  *

  SKIP_SIBLINGS ?When preVisitDirectory returns this value, the specified directory is not visited, postVisitDirectory is not invoked, and no further unvisited siblings are visited. If returned from the postVisitDirectory method, no further siblings are visited. Essentially, nothing further happens in the specified directory.

  *

  TERMINATE ?Immediately aborts the file walking. No further file walking methods are invoked after this value is returned.

  *

  SKIP_SUBTREE ?When preVisitDirectory returns this value, the specified directory and its subdirectories are skipped. This branch is "pruned out" of the tree.

  Note:To walk a file tree, you first need to implement a FileVisitor. A FileVisitor specifies the required behavior at key points in the traversal process: when a file is visited, before a directory is accessed, after a directory is accessed, or when a failure occurs.

  Reference: The Java Tutorials,Walking the File Tree

• Question 90:

  How many Threads are created when passing tasks to an Executor Instance?

  A. A new Thread is used for each task.
  B. A number of Threads equal to the number of CPUs is used to execute tasks.
  C. A single Thread is used to execute all tasks.
  D. A developer-defined number of Threads Is used to execute tasks.
  E. A number of Threads determined by system load is used to execute tasks.
  F. The method used to obtain the Executor determines how many Threads are used to execute tasks.
  F. The method used to obtain the Executor determines how many Threads are used to execute tasks.

  ---

  A simple way to create an executor that uses a fixed thread pool is to invoke the newFixedThreadPool factory method in java.util.concurrent.Executors This class also provides the following factory methods:

  *

  The newCachedThreadPool method creates an executor with an expandable thread pool. This executor is suitable for applications that launch many short-lived tasks.

  *

  The newSingleThreadExecutor method creates an executor that executes a single task at a time.

  *

  Several factory methods are ScheduledExecutorService versions of the above executors.

  If none of the executors provided by the above factory methods meet your needs, constructing instances of java.util.concurrent.ThreadPoolExecutor or

  java.util.concurrent.ScheduledThreadPoolExecutor will give you additional options.

  Note:The Executor interface provides a single method, execute, designed to be a drop-in replacementfor a common thread-creation idiom. If r is a Runnable object, and e is an Executor object you can replace

  (new Thread(r)).start();

  with

  e.execute(r);

  However, the definition of execute is less specific. The low-level idiom creates a new thread and launches it immediately. Depending on the Executor implementation, execute may do the same thing, but is more likely to use an existing worker

  thread to run r, or to place r in a queue to wait for a worker thread to become available.

  Reference: The Java Tutorials,Thread Pools

  Reference: The Java Tutorials,Executor Interfaces