Oracle 1Z0-804 Online Practice Questions and Exam Preparation

Oracle 1Z0-804 Online Questions & Answers

• Question 61:

  Given:

  ConcurrentMap PartList = new ConcurrentMap<>();

  Which fragment puts a key/value pair in partList without the responsibility of overwriting an existing key?

  A. partList.out(key, "Blue Shirt");
  B. partList.putIfAbsent(key, "Blue Shirt");
  C. partList.putIfNotLocked (key, "Blue Shirt");
  D. partList.putAtomic(key, "Blue Shirt")
  E. if (!partList.containsKey(key)) partList.put (key, "Blue Shirt");
  B. partList.putIfAbsent(key, "Blue Shirt");

  ---

  putIfAbsent(K key, V value)

  If the specified key is not already associated with a value, associate it with the given value.

  Reference: java.util.concurrent , Interface ConcurrentMap

• Question 62:

  Which two actions can be used in registering a JDBC 3.0 driver?

  A. Add the driver class to the META-INF/services folder of the JAR file.
  B. Set the driver class name by using the jdbc.drivers system property.
  C. Include the JDBC driver class in a jdbcproperties file.
  D. Use the java.lang.class.forName method to load the driver class.
  E. Use the DriverManager.getDriver method to load the driver class.
  A. Add the driver class to the META-INF/services folder of the JAR file.
  D. Use the java.lang.class.forName method to load the driver class.

  ---

  A: f your JDBC Driver is NOT JDBC 4-compliant then we can update the driver using "jar" utility by adding the "META-INF/services/java.sql.Driver" inside it. as following:

  D: Dynamic loading of Java classes at runtime provides tremendous flexibility in the development of enterprise systems. It provides for the basis of "application servers", and allows even simpler, lighter-weight systems to accomplish some of the same ends. Within Java, dynamic-loading is typically achieved by calling the forName method on the class java.lang.Class

• Question 63:

  Given:

  public class Test {

  public static void main(String[] args) {

  String[] arr = {"SE","ee","ME"};

  for(String var : arr) {

  try {

  switch(var) {

  case "SE":

  System.out.println("Standard Edition");

  break;

  case "EE":

  System.out.println("Enterprise Edition");

  break;

  default: assert false;

  }

  } catch (Exception e) {

  System.out.println(e.getClass()); }

  }

  }

  }

  And the commands:

  javac Test.java

  java -ea Test

  What is the result?

  A. Compilation fails
  B. Standard Edition Enterprise Edition Micro Edition
  C. Standard Edition class java.lang.AssertionError Micro Edition
  D. Standard Edition is printed and an Assertion Error is thrown
  C. Standard Edition class java.lang.AssertionError Micro Edition

  ---

  The command line :

  javac Test.java

  will compile the program.

  As for command line:

  java -ea Test

  First the code will produce the output:

  Standard Edition

  See Note below.

  The -ea option will enable assertions.

  This will make the following line in the switch statement to be run:

  default: assert false;

  This will thow an assertion error. This error will be caught.

  An the class of the assertion error (class java.lang.AssertionError) will be printed by the following line:

  System.out.println(e.getClass());

  Note: The java tool launches a Java application. It does this by starting a Java runtime environment, loading a specified class, and invoking that class's main method. The method declaration must look like the following:

  public static void main(String args[])

  Paramater -ea:

  -enableassertions[:"..." | : ]

  -ea[:"..." | : ]

  Enable assertions. Assertions are disabled by default.

  With no arguments, enableassertions or -ea enables assertions.

  Note 2:

  An assertion is a statement in the JavaTM programming language that enables you to test your assumptions about your program.

  Each assertion contains a boolean expression that you believe will be true when the assertion executes. If it is not true, the system will throw an error.

  public class AssertionError

  extends Error

  Thrown to indicate that an assertion has failed.

  Note 3:

  The javac command compiles Java source code into Java bytecodes. You then use the Java interpreter - the java command - to interprete the Java bytecodes.

  Reference: java - the Java application launcher

  Reference: java.lang Class AssertionError

• Question 64:

  View the exhibit: (*Missing*)

  Given the code fragment:

  class Finder extends SimpleFileVisitor {

  private final PathMatcher matcher;

  private static int numMatches = 0;

  Finder () {

  matcher = FileSystems.getDefault().getPathMatcher("glob:*java");

  }

  void find(Path file) {

  Path name = file.getFileName();

  if (name != null andand matcher.matches(name)) {

  numMatches++;

  }

  }

  void report()

  {

  System.out.println("Matched: " + numMatches);

  }

  @Override

  public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)

  find(file);

  return CONTINUE;

  }

  }

  public class Visitor {

  public static void main(String[] args) throws IOException {

  Finder finder = new Finder();

  Files.walkFileTree(Paths.get("D:\\Project"), finder);

  finder.report();

  }

  }

  What is the result?

  A. Compilation fails
  B. 6
  C. 4
  D. 1
  E. 3
  F. Not possible to answer due to missing exhibit.
  F. Not possible to answer due to missing exhibit.

  ---

  Note: The FileSystems.getDefault() returns the default FileSystem. The default file system creates objects that provide access to the file systems accessible to the Java virtual machine. The working directory of the file system is the current user directory, named by the system property user.dir.

• Question 65:

  Given:

  public class Dog {

  protected String bark() {return "woof "; }

  }

  public class Beagle extends Dog {

  private String bark() { return "arf "; }

  }

  public class TestDog {

  public static void main(String[] args) {

  Dog[] dogs = {new Dog(), new Beagle()};

  for(Dog d: dogs)

  System.out.print(d.bark());

  }

  }

  What is the result?

  A. woof arf
  B. woof woof
  C. arf arf
  D. A RuntimeException is generated
  E. The code fails to compile
  A. woof arf

• Question 66:

  Given:

  Deque myDeque = new ArrayDeque();

  myDeque.push("one");

  myDeque.push("two");

  myDeque.push("three");

  System.out.println(myDeque.pop());

  What is the result?

  A. Three
  B. One
  C. Compilation fails.
  D. The program runs, but prints no output.
  A. Three

• Question 67:

  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 methods.
  E. Make the add, delete, and find, and update methods private for encapsulation.
  F. Make the getName and getID methods private for 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 methods.

  ---

  C: The methods related directly to the entity Customer is moved to a new class.

  D: Example (here Customer is the main entity):

  public class Customer {

  private final String id;

  private String contactName;

  private String phone;

  public void setId(String id) { this.id = id; }

  public String getId() { return this.id; }

  public void setContactName(String cn) { this.contactName = cn;}

  public String getContactName() { return this.contactName; }

  public void setPhone(String phone) { this.phone = phone; }

  public String getPhone() { return this.phone; }

  }

  public interface CustomerDAO {

  public void addCustomer(Customer c) throws DataAccessException;

  public Customer getCustomer(String id) throws DataAccessException;

  public List getCustomers() throws DataAccessException;

  public void removeCustomer(String id) throws DataAccessException;

  public void modifyCustomer(Customer c) throws DataAccessException;

  }

  Note: DAO Design Pattern

  *

  Abstracts and encapsulates all access to a data source

  *

  Manages the connection to the data source to obtain and store data

  *

  Makes the code independent of the data sources and data vendors (e.g. plain-text, xml, LDAP, MySQL, Oracle, DB2)

  

• Question 68:

  Given the class?

  public class Name implements Comparable {

  String first, last;

  public Name(String first, String last) {

  this.first = first;

  this.last = last;

  }

  public int compareTo (Name n) {

  int cmpLast = last.compareTo(n.last);

  return cmpLast != 0 ? cmpLast : first.compareTo(n.first);

  }

  public String toString() {

  return first + " " + last;

  }

  }

  and the code fragment:

  ArrayList list = new ArrayList();

  list.add (new Name("Joe","Shmoe"));

  list.add (new Name("John","Doe"));

  list.add (new Name("Jane","Doe"));

  Collections.sort(list);

  for (Name n : list) {

  System.out.println(n);

  }

  What is the result?

  A. Jane Doe John Doe Joe Shmoe
  B. John Doe Jane Doe Joe Shmoe
  C. Joe Shmoe John Doe Jane Doe
  D. Joe Shmoe Jane Doe John Doe
  E. Jane Doe Joe Shmoe John Doe
  F. John Doe Joe Shmoe Jane Doe
  A. Jane Doe John Doe Joe Shmoe

  ---

  The list will be sorted alpabethically. Output will be: Jane Doe John Doe Joe Shmoe

• Question 69:

  Given:

  public class Runner {

  public static String name = "unknown";

  public void start() {

  System.out.println(name);

  }

  public static void main(String[] args) {

  name = "Daniel";

  start();

  }

  }

  What is the result?

  A. Daniel
  B. Unknown
  C. It may print "unknown" or "Daniel" depending on the JVM implementation.
  D. Compilation fails.
  E. An exception is thrown at runtime.
  D. Compilation fails.

  ---

  The compilation fails at line start();

  Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - non- static method start() cannot be referenced from a static context

• Question 70:

  Which code fragment is required to load a JDBC 3.0 driver?

  A. DriverManager.loadDr iver ("org.xyzdata.jdbc.NetworkDriver");
  B. Class.forName("org.xyzdata.jdbc-NetworkDriver");
  C. Connection con = Connection.getDriver ("jdbc:xyzdata://localhost:3306/EmployeeDB");
  D. Connection con = DriverManager.getConnection ("jdbc:xyzdata://localhost:3306/EmployeeDB");
  B. Class.forName("org.xyzdata.jdbc-NetworkDriver");

  ---

  In previous versions (prior to 4.0) of JDBC, to obtain a connection, you first had to initialize your JDBC driver by calling the method Class.forName. This methods required an object of type java.sql.Driver.

  Note:

  DriverManager: This fully implemented class connects an application to a data source, which is specified by a database URL. When this class first attempts to establish a connection, it automatically loads any JDBC 4.0 drivers found within

  the class path. Note that your application must manually load any JDBC drivers prior to version 4.0.