Oracle Professional Java Exam Questions (OCJA:1z0-809)

Oracle Professional Java Exam Questions (OCJA:1z0-809) 


by Rocky Jagtiani
 Oracle Certified Professional in Java
(cleared OCPJP6 : 1Z0-851 in 2012 with 94%)
I train on Oracle Certifications from last 7 years
My training's are listed on https://training.suven.net


This article is split into 2 blog post. This is the second post. First post has questions on OCJA:1z0-808.
This post is 45 mins read only.

To re-assess my skills, I decided to give the OCJA:1z0-808 exam this month. Gave some International certification exams after a long time. Happy to clear OCJA:1z0-808 with 89% and OCJP:1z0-809 with 83%. The purpose of this blog-post is to highlight different types of Java problems, I mean programs one to would have to solve for clearing the Java Certification exams. You can find the 1z0-808 and 1z0-809 exam specs under "Course highlights" section here.

To run any of the programs on this blog-post , you may click here
  
Before you run any of the programs , try solving them without running on a online Java compiler.
You can even copy-paste these programs on your local machine and run them, but first try solving using only your own brains.

Tips :
  1. Time yourself well. Solve each problem with in 1.5 mins.
  2. Don't use paper and pen. Solve in your mind.
  3. Avoid all distractions like whatsapp, fb or ... . Lock your self in a study room and solve.   
All the best. Let's start !!

1) Consider the following program:
import java.math.BigDecimal;
class NumberTest {
public static void main(String []args) {
Number [] numbers = new Number[4];
numbers[0] = new Number(0); // NUM
numbers[1] = new Integer(1);
numbers[2] = new Float(2.0f);
numbers[3] = new BigDecimal(3.0); // BIG
for(Number num : numbers) {
System.out.print(num + " ");
}}}

Which one of the following options correctly describes the behavior of this program?
a) Compiler error in line marked with comment NUM because Number cannot be
instantiated.
b) Compiler error in line marked with comment BIG because BigDecimal does not
inherit from Number.
c) When executed, this program prints the following: 0 1 2.0 3.
d) When executed, this program prints the following: 0.0 1.0 2.0 3.0.
------------------------------------------

2) What will be the output of the following program?
class Base {
public Base() {
System.out.println("Base");
}
}
class Derived extends Base {
public Derived() {
System.out.println("Derived");
}
}
class DeriDerived extends Derived {
public DeriDerived() {
System.out.println("DeriDerived");
}
}
class Test {
public static void main(String []args) {
Derived b = new DeriDerived();
}
}

Options
a) Base
Derived
DeriDerived

b) Derived
DeriDerived

c) DeriDerived
Derived
Base

d) DeriDerived
Derived
------------------------------------------

3) Consider the following program:
class Base {
public Base() {
System.out.print("Base ");
}
public Base(String s) {
System.out.print("Base: " + s);
}
}
class Derived extends Base {
public Derived(String s) {
super(); // Stmt-1
super(s); // Stmt-2
System.out.print("Derived ");
}
}
class Test {
public static void main(String []args) {
Base a = new Derived("Hello ");
}
}
Select three correct options from the following list:
a) Removing Stmt-1 will make the program compilable and it will print the following:
Base Derived.
b) Removing Stmt-1 will make the program compilable and it will print the following:
Base: Hello Derived.
c) Removing Stmt-2 will make the program compilable and it will print the following:
Base Derived.
d) Removing both Stmt-1 and Stmt-2 will make the program compilable and it will print
the following: Base Derived.
e) Removing both Stmt-1 and Stmt-2 will make the program compilable and it will print
the following: Base: Hello Derived.
------------------------------------------

4) Consider the following program and choose the correct option from the list of options:
class Base {
public void test() {}
}
class Base1 extends Base {
public void test() {
System.out.println("Base1");
}
}
class Base2 extends Base {
public void test() {
System.out.println("Base2");
}
}
class Test {
public static void main(String[] args) {
Base obj = new Base1();
((Base2)obj).test(); // CAST
}
}
a) The program will print the following: Base1.
b) The program will print the following: Base2.
c) The compiler will report an error in the line marked with comment CAST.
d) The program will result in an exception (ClassCastException). 
------------------------------------------

5) Consider the following program:
interface EnumBase { }
enum AnEnum implements EnumBase { // IMPLEMENTS_INTERFACE ONLY_MEM;
}
class EnumCheck {
public static void main(String []args) {
if(AnEnum.ONLY_MEM instanceof AnEnum) {
System.out.println("yes, instance of AnEnum");
}
if(AnEnum.ONLY_MEM instanceof EnumBase) {
System.out.println("yes, instance of EnumBase");
}
if(AnEnum.ONLY_MEM instanceof Enum) { // THIRD_CHECK
System.out.println("yes, instance of Enum");
}
}
}


Which one of the following options is correct?
a) This program results in a compiler error in the line marked with comment IMPLEMENTS_INTERFACE.
b) This program results in a compiler error in the line marked with comment THIRD_CHECK.
c) When executed, this program prints the following:
yes, instance of AnEnum
d) When executed, this program prints the following:
yes, instance of AnEnum
yes, instance of EnumBase
e) When executed, this program prints the following:
yes, instance of AnEnum
yes, instance of EnumBase
yes, instance of Enum
------------------------------------------

6) Consider the following program:
class WildCard {
interface BI {}
interface DI extends BI {}
interface DDI extends DI {}
static class C {}
static void foo(C arg) {}
public static void main(String []args) {
foo(new C()); // ONE
foo(new C()); // TWO
foo(new C()); // THREE
foo(new C()); // FOUR
}
}

Which of the following options are correct?
a) Line marked with comment ONE will result in a compiler error.
b) Line marked with comment TWO will result in a compiler error.
c) Line marked with comment THREE will result in a compiler error.
d) Line marked with comment FOUR will result in a compiler error.
------------------------------------------

 7) In the context of Singleton pattern, which one of the following statements is true?
a) A Singleton class must not have any static members.
b) A Singleton class has a public constructor.
c) A Factory class may use Singleton pattern.
d) All methods of the Singleton class must be private.

In the context of Singleton pattern, which one of the following statements is true?
a) A Singleton class must not have any static members.
b) A Singleton class has a public constructor.
c) A Factory class may use Singleton pattern.
d) All methods of the Singleton class must be private.
------------------------------------------

8) Which one of the following class definitions will compile without any errors?

 a) class P {
static T s_mem;
}

b) class Q {
T mem;
public Q(T arg) {
mem = arg;
}
}

c) class R {
T mem;
public R() {
mem = new T();
}
}

d) class S {
T []arr;
public S() {
arr = new T[10];
}
}
------------------------------------------

9) Which one of the following interfaces declares a single method named iterator()?
(Note: Implementing this interface allows an object to be the target of the for-each statement.)
a) Iterable
b) Iterator
c) Enumeration
d) ForEach
------------------------------------------

10) Consider the following program:
import java.util.*;
class ListFromVarargs {
public static List asList1(T... elements) {
ArrayList temp = new ArrayList<>();
for(T element : elements) {
temp.add(element);
}
return temp;
}
public static List asList2(T... elements) {
ArrayList temp = new ArrayList<>();
for(T element : elements) {
temp.add(element);
}
return temp;
}
public static List asList3(T... elements) {
ArrayList temp = new ArrayList<>();
for(T element : elements) {
temp.add(element);
}
return temp;
}
public static List asList4(T... elements) {
List temp = new ArrayList();
for(T element : elements) {
temp.add(element);
}
return temp;
}
}

Which of the asList definitions in this program will result in a compiler error?
a) The definition of asList1 will result in a compiler error.
b) The definition of asList2 will result in a compiler error.
c) The definition of asList3 will result in a compiler error.
d) The definition of asList4 will result in a compiler error.
e) None of the definitions (asList1, asList2, asList3, asList4) will result in a compiler error.
------------------------------------------

11) Consider the following program:
import java.util.*;
class TemplateType {
public static void main(String []args) {
List, List>> list =
new ArrayList<>(); // ADD_MAP
Map, List> map = new HashMap<>();
list.add(null); // ADD_NULL
list.add(map);
list.add(new HashMap,
List>()); // ADD_HASHMAP
for(Map element : list) { // ITERATE
System.out.print(element + " ");
}}}

Which one of the following options is correct?
a) This program will result in a compiler error in line marked with comment ADD_MAP.
b) This program will result in a compiler error in line marked with comment ADD_HASHMAP.
c) This program will result in a compiler error in line marked with comment ITERATE.
d) When run, this program will crash, throwing a NullPointerException in line marked with comment ADD_NULL.
e) When run, this program will print the following: null {} {}
------------------------------------------

12) Which of the following statements are true about java.sql.Savepoint? (select all that apply)
a) Savepoint is a point within the current transaction that can be referenced from the  Connection.rollback() method
b) When a transaction is rolled back to a savepoint all changes made after that savepoint are undone.
c) Savepoints must be named. It is not possible to have "unnamed savepoints".
d) java.sql.Savepoint is an abstract class; it is implemented by the classes such as JDBCSavepoint, ODBCSavepoint, and TransactionSavepoint in the java.sql package.
------------------------------------------

13) Consider the following program and choose the appropriate option:
import java.util.*;
class Test {
public static void main(String []args) {
Map map =
new HashMap(); //#1
Map map2 =
new HashMap(); //#2
Map map3 = new HashMap<>(); //#3
Map<> map4 = new HashMap(); //#4
}
}
a) Statement #1 and #2 will compile successfully.
b) Statement #2 and #3 will compile successfully.
c) Statement #3 and #4 will compile successfully.
d) Statement #4 and #1 will compile successfully. 
------------------------------------------

14)  Which of the following statements are true regarding the classes or interfaces defined in the java.util.concurrent package?
a) The Executor interface declares a single method execute(Runnable command) that executes the given command at sometime in the future.
b) The Callable interface declares a single method call() that computes a result.
c) The Exchanger class provides a “synchronization point at which threads can pair and swap elements within pairs”.
d) The TimeUnit enumeration represents time duration and is useful for specifying timing parameters in concurrent programs.
------------------------------------------

15) Consider the following program and predict the output:
import java.util.regex.*;
class Test {
public static void main(String[] args) {
String str1 = "xxzz";
String str2 = "xyz";
String str3 = "yzz";
Pattern pattern = Pattern.compile("(xx)*y?z{1,}");
Matcher matcher = pattern.matcher(str1);
System.out.println(matcher.matches());
System.out.println(pattern.matcher(str2).matches());
System.out.println(
Pattern.compile("(xx)*y?z{1,}").
matcher(str3).matches());
}
}

a) true
    false
    true

b) true
    false
    false

c) false
    false
    false

d) false
    false
    true

e) true
    true
    true 
------------------------------------------

16) Consider the following program and predict the output:
import java.util.regex.*;
class Test {
public static void main(String[] args) {
String str =
"Suneetha N.=9876543210, Pratish Patil=9898989898";
Pattern pattern =
Pattern.compile("(\\w+)(\\s\\w+)(=)(\\d{10})");
Matcher matcher = pattern.matcher(str);
String newStr = matcher.replaceAll("$4:$2,$1");
System.out.println(newStr);
}
}
a) 9876543210: N.,Suneetha, 9898989898: Patil,Pratish
b) Suneetha N.=9876543210, Pratish Patil=9898989898
c) Suneetha N.=9876543210, 9898989898: Patil,Pratish
d) This program throws a runtime exception.
------------------------------------------

17) Consider the following program:
import java.util.*;
class Format {
public static void main(String []args) {
Formatter formatter = new Formatter();
Calendar calendar = Calendar.getInstance(Locale.US);
calendar.set(/* year =*/ 2012, /* month = */ Calendar.FEBRUARY, /* date = */ 1);
formatter.format("%tY/%
System.out.println(formatter);
}
}
Which one of the following options correctly describes the behavior of this program?
a) The program throws a MissingFormatArgumentException.
b) The program throws an UnknownFormatConversionException.
c) The program throws an IllegalFormatConversionException.
d) The program prints the following: 12/February/01. 
------------------------------------------

18) Consider the following program:
import java.util.*;
public class ResourceBundle_it_IT extends ListResourceBundle {
public Object[][] getContents() {
return contents;
}
static final Object[][] contents = {
{ "1", "Uno" },
{ "2", "Duo" },
{ "3", "Trie" },
};
public static void main(String args[]) {
ResourceBundle resBundle =
ResourceBundle.getBundle("ResourceBundle", new Locale("it", "IT", ""));
System.out.println(resBundle.getObject(new Integer(1).toString()));
}
}
Which one of the following options correctly describes the behavior of this program?
a) This program prints the following: Uno.
b) This program prints the following: 1.
c) This program will throw a MissingResourceException.
d) This program will throw a ClassCastException.
------------------------------------------

19) 
import java.util.*;
import java.util.concurrent.*;
class SortedOrder {
public static void main(String []args) {
Set set = new CopyOnWriteArraySet(); // #1
set.add("2");
set.add("1");
Iterator iter = set.iterator();
set.add("3");
set.add("-1");
while(iter.hasNext()) {
System.out.print(iter.next() + " ");
}}}

Which one of the following options correctly describes the behavior of this program?
a) The program prints the following: 2 1.
b) The program prints the following: 1 2.
c) The program prints the following: -1 1 2 3.
d) The program prints the following: 2 1 3 -1.
e) The program throws a ConcurrentModificationException
f ) This program results in a compiler error in statement #1
------------------------------------------

20) Consider the following program:
import java.io.*;
class CloseableImpl implements Closeable {
public void close() throws IOException {
System.out.println("In CloseableImpl.close()");
}
}
class AutoCloseableImpl implements AutoCloseable {
public void close() throws Exception {
System.out.println("In AutoCloseableImpl.close()");
}
}
class AutoCloseCheck {
public static void main(String []args) {
try (Closeable closeableImpl = new CloseableImpl();
AutoCloseable autoCloseableImpl
= new AutoCloseableImpl()) {
} catch (Exception ignore) {
// do nothing
}
finally {
// do nothing
}
}
}
Which one of the following options correctly shows the output of this program when the program is executed?
a) This program does not print any output in console.
b) This program prints the following output:
In AutoCloseableImpl.close()
c) This program prints the following output:
In AutoCloseableImpl.close()
In CloseableImpl.close()
d) This program prints the following output:
In CloseableImpl.close()
In AutoCloseableImpl.close()
------------------------------------------

 21)  Consider the following program and predict the output:
import java.nio.file.*;
class PathInfo {
public static void main(String[] args) {
// assume that the current directory is "D:\workspace\ch14-test"
Path testFilePath = Paths.get(".\\Test");
System.out.println("file name:" + testFilePath.getFileName());
System.out.println("absolute path:" + testFilePath.toAbsolutePath());
System.out.println("Normalized path:" + testFilePath.normalize());
}
}

a) file name:Test
absolute path:D:\workspace\ch14-test\.\Test
Normalized path:Test

b) file name:Test
absolute path:D:\workspace\ch14-test\Test
Normalized path:Test

c) file name:Test
absolute path:D:\workspace\ch14-test\.\Test
Normalized path:D:\workspace\ch14-test\.\Test

d) file name:Test
absolute path:D:\workspace\ch14-test\.\Test
Normalized path:D:\workspace\ch14-test\Test
------------------------------------------

 22) Which one of the following statement is NOT correct?
a) You need to use a Statement when you need to send a SQL statement to the database
without any parameter.
b) PreparedStatement represents a precompiled SQL statement.
c) PreparedStatement can handle IN and OUT parameters.
d) CallableStatement is used to execute stored procedures.
------------------------------------------

 23) Consider the following program and choose the right option:
import java.util.Locale;
class Test {
public static void main(String []args) {
Locale locale1 = new Locale("en"); //#1
Locale locale2 = new Locale("en", "in"); //#2
Locale locale3 = new Locale("th", "TH", "TH"); //#3
Locale locale4 = new Locale(locale3); //#4
System.out.println(locale1 + " " + locale2 + " " + locale3 + " " + locale4);
}
}

a) This program will print the following: en en_IN th_TH_TH_#u-nu-thaith_TH_TH_#u-nu-thai.
b) This program will print the following: en en_IN th_TH_TH_#u-nu-thai
    (followed by a runtime exception).
c) This program results in a compiler error at statement #1.
d) This program results in a compiler error at statement #2.
e) This program results in a compiler error at statement #3.
f ) This program results in a compiler error at statement #4.
------------------------------------------
Explanation to just few problems :
------------------------------------------

Ans 5) e) When executed, this program prints the following:
yes, instance of AnEnum
yes, instance of EnumBase
yes, instance of Enum
An enumeration can implement an interface (but cannot extend a class, or cannot be a base class). Each enumeration constant is an object of its enumeration type. An enumeration automatically extends the abstract class java.util.Enum.
Hence, all the three instanceof checks succeed.

Ans 8)  b) class Q {
T mem;
public Q(T arg) {
mem = arg;
}
}
Option a): You cannot make a static reference of type T.
Option c) and d): You cannot instantiate the type T or T[] using new operator.

Ans 10)  b) The definition of asList2 will result in a compiler error.
In the asList2 method definition, temp is declared as ArrayList. Since the template type is a wild-card, you cannot put any element (or modify the container). Hence, the method call temp.add(element);  will result in a compiler error. 

Ans 16)  c) Suneetha N.=9876543210, 9898989898: Patil,Pratish
The first contact does not match with the specified regex (since "." is not covered by "\w+"); hence, the first part of the string is unchanged. The second part of string matches with the specified regex, so the replace rearranges the substring.

Ans 23)  f ) This program results in a compiler error at #4.
The Locale class supports three constructors that are used in statements #1, #2, and #3; however, there is no constructor in the Locale class that takes another Locale object as
argument, so the compiler gives an error for statement #4.
----------------------
more sample questions are given here
----------------------

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