Elance JAVA Test Answers 2015



A function that defines the steps necessary to instantiate one object of that class is called:
an instantiator.
a destructor.
a constructor.


What does the synchronized keyword on a method do?
Uses the object's intrinsic lock to prevent two threads from accessing the method simultaneously.
Creates a new semaphore to prevent two threads from accessing the method simultaneously.
Prevents objects outside the current package from accessing the method.
Ensures that each call to a synchronized method is run in a separate thread.


Given the code: Integer i= new Integer("1"); if (i.toString() == i.toString()) System.out.println("Equal"); else System.out.println("Not Equal");
Prints "Equal"
None of the above
Compiler error
Prints "Not Equal"


Consider the following code: int i=aReader.read(); What is the true of the type of variable aReader?
It has to be a FileReader
It can either be a FileReader or a BufferReader.
It can neither be a FileReader or a BufferReader.
It has to be a BufferReader.


If "A" is a class, then what does the statement "A a1;" do?
The statement does not do anything.
An object 'a1' of class 'A' is created.
The object reference variable 'a1' should be in title case.
The syntax is incorrect.
The object reference variable 'a1' is declared.


What is displayed when the following code is compiled and executed? String s1 = new String("Test"); String s2 = new String("Test"); if (s1==s2) System.out.println("Same"); if (s1.equals(s2)) System.out.println("Equals");
Same
Equals
Same Equals
The code compiles, but nothing is displayed upon execution.


Do we need to import the java.lang package at anytime?
No
Yes


The pattern described below is known as: public class Foo{ private static Foo instance; private Foo(){ } private static getInstance(){ if (instance == null){ instance = new Foo(); } return instance; }
the Singleton pattern
the Observer Pattern
the Flyweight pattern
the Factory pattern


Suppose ArrayList x contains two strings [Beijing, Singapore]. Which of the following methods will cause the list to become [Beijing, Chicago, Singapore]?
x.add(1, "Chicago")
x.add(0, "Chicago")
x.add(2, "Chicago")
x.add("Chicago")


Which statement is wrong?
ArrayList<Integer> myList = new ArrayList<Integer>();
ArrayList<Double> myList = new ArrayList<Double>();
ArrayList<String> myList = new ArrayList<Integer>();
ArrayList<String> myList = new ArrayList<String>();
ArrayList<String> myList = new ArrayList<String>(10);


Under the strictest definition, an interface may contain only:
constructors
fields
additional pylons
abstract methods


which of the following is a correct statement:
a class can inherit multiple abstract superclass
a class can implement multiple interface
a class can inherit multiple superclass


What is the syntax for creating a class derived from the class named MyClass?
public class MyDerived : MyClass
class MyDerived implements MyClass
class MyDerived extends MyClass


When you run a Java program, the system is running the Java Runtime Engine (JRE) as an executable which then:
process the java code through the interpreter which is pointed to by the CLASSPATH statement.
processes the java code through the Java Virtual Machine (JVM).
none of these
processes the java code through the native OS interpreter.


Consider public class MyClass{ public MyClass(){/*code*/} // more code... } To instantiate MyClass, you would write?
MyClass mc = new MyClass();
MyClass mc = MyClass();
MyClass mc = MyClass;
It can't be done. The constructor of MyClass should be defined as public void MyClass(){/*code*/}
MyClass mc = new MyClass;


_____ jumps out of an entire loop, whereas _____ jumps to the next iteration.
stop; jump
stop; continue
break; continue
break; jump


Consider the following code snippet String river = new String(“Columbia”); System.out.println(river.length()); What is printed?
7
Columbia
8
6
river


The correct operator for 'conditional or' is:
&
||
|
&&


Do you need to explicitly define a constructor for every class?
Yes
No


public class Dog extends Animal{ ... } is an example of...
Encapsulation
Abstraction
Type casting
Inheritance


Which keywords would you use to handle exceptions in Java?
try, catch, end
throw, catch, do
throw, take, finally
try, catch, finally
throw, catch, end


Class definitions in Java can have which of the following access levels?
private
protected
public
all of these


All Java files must have a .java extension and are compiled with the:
system runtime compiler
javac compiler
gcc compiler


An applet can do which of the following?
Self initialize
Stop running
Start running
All of these


Which of the following is the correct signature for a main method that can be used as an entry point by the Java runtime?
public void main(String[] args)
public static int main(String[] args)
public static void main(Collection<String> c)
public static void main(String[] args)


The varargs method: public void foo(String... strings) may be called with:
foo("bar1", "bar2", "bar3");
foo("bar1", "bar2");
All of these.
foo("bar1");


The process of changing a datatype of a value is called:
typecasting
hardcasting
datatyping


What is the proper syntax for a Java class's main method?
private static void main(String[] args)
public static void main(String[] args)
private void main (String[] args)
public static main(String[] args)
public void static main(String[] args)


What are the core JMS-related objects required for each JMS-enabled application?
Within a session, the appropriate sender or publisher or receiver or subscriber objects.
All of these
A connection object provided by the JMS server (the message broker)
Within a connection, one or more sessions, which provide a contest for message sending and receiving


A JavaBean is a special Java class:
which must be serializable so that the state can be stored.
all of these
which must follow standard naming conventions for attributes such as getXxxx.
which must have a public, no-argument constructor.


Which of these keywords is used to define packages in Java?
pack
pkg
Package
Pkg
package


Which of the following is correct way of importing an entire package ‘pkg’?
import pkg
Import pkg.*
import pkg.*
Import pkg


How do you declare a destructor in Java?
myClass::~myClass();
You don't need a destructor
@destructor myClass(){ }
@Override System.gc(){ }


You can use the 'static' keyword for which of the following?
Classes
All of these
Methods
Variables


As a general syntax rule, Java is case sensitive on:
all platforms.
only Microsoft Windows platforms.
only on UNIX based platforms.


Can an interface have member variables?
No, never
Yes, as long as they are public, static and final


Will a program run if the main() is not static?
No
Yes


What keyword is used to add external package members to the current Java file?
import
using
get
add
uses


Which of the following JNDI properties provide security information?
java.naming.security.principal
All of these
java.naming.security.credential
java.naming.security.authentication


What company developed java?
IBM
Facebook
Sun Microsystems (Oracle)
Google
Microsoft


Which of the following is correct for the "main" method of a class?
@Main public void main(int argc, String[] argv) {}
public static void main(String [] args) { }
public void main(int argc, String [] argv) {}
public final void main(String arg0, String arg1="default") {}


What effect does declaring a method as final have?
The method can only accept final parameters.
The return value of the method will be final.
The parameters passed to the method cannot be modified.
The method cannot be overridden in subclasses.


How do you prevent a class from being extended by a subclass?
Declare all its members as private.
Declare the class as abstract.
Declare all member variables and methods as protected.
Declare the class as final.


You read the following statement in a valid Java program: submarine.dive(depth); What must be true?
"dive" must be a method.
"dive" must be the name of an instance field.
"submarine" must be a method.
"submarine" must be the name of a class.
"depth" must be an int.


What's wrong with the following method: public static int getSize(){ int temp = super.getSize(); if(temp==0) temp=this.size; return temp; }
static methods cannot refer to "this" or "super"
static methods cannot return type "int"
There is nothing wrong with this method.


Are primitive data types passed by reference or passed by value?
Passed by reference
Passed by value


________ is when a subclass implements a method that is already provided by a superclass.
Method overriding
Method overloading
Method overdriving
Object orientation overdev


If I write return at the end of the try block, will the finally block still execute?
No
Yes


What is a token?
A token is a group of digits
A token is a group of characters that means something in a particular context.
A token is any character that may be used as punctuation
A token is a type of expression


What will be the output of below code String a="abc"; String b="abc"; String c=new String("abc"); if(a==c && a.equals(b)){ System.out.println("They are equal"); } else System.out.println("They are not equal");
They are not equal
They are equal


A deadlock error occurs when a Java program
has a for loop or while loop that can never satisfy its condition, causing the loop to run forever and the program to wait indefinitely.
has a circular try-catch block, in which the catch results in the catch block being reached again repeatedly, causing the program to run indefinitely.
has a circular dependency on 2 or more synchronized objects, causing one of the objects to wait indefinitely.


The StringBuffer and StringBuilder classes in Java are optimized for
retrieval of all or part of a string but not altering the string.
creating strings which change considerably.
creating strings which only change once.


Java allows you to specify two types of variables: primitive, which store a single value, and
reference, where the data is accessed indirectly.
neither of these
wide, which reference a double byte variable.


The "synchronized" keyword does the following
Prevents concurrency within methods or statements
Aligns samples within the JVM for accuracy when profiling
Prohibits code from being executed during garbage collection
Provides a convenient shortcut for creating threads
Ensures that each call finishes at the same time


Which Map implementation is safe for modification in a multi-threaded program?
java.util.concurrent.ConcurrentHashMap
java.util.TreeMap
java.util.LinkedHashMap
java.util.WeakHashMap


Can you mark an interface as final?
Yes
No


A method is considered to be overloaded when:
You cannot overload a method
the method throws an exception
they have multiple call signatures
they have different return types


Can a class be both abstract and final?
Yes
No


Can you declare an abstract class with no abstract methods?
No
Yes


What is the output of the below code ? int a = 0; int b = 0; if (a++ == 1 || b++ == 1) {} System.out.println(a + " " + b);
0 0
0 1
1 0
1 1


Can we override a static method?
Yes
No


Can static and abstract keywords be used together?
No
Yes


Which one of these primitive types is unsigned?
long
double
int
char
float


Java programs must have at least one method called main() _____.
Both of these
In order to compile
In order to execute


TreeMap class is used to implement which collection interface?
List
SortedMap
SortedSet
Set


What is transient variable?
It is the default variable in the class.
A variable which is not static.
A variable which is not serialized.
A variable which is serialized.


Java interfaces can extend...
nothing: extension is not valid for interfaces.
multiple interfaces.
final classes.
one other interface.


Which of the following is *not* a method in java.lang.String?
String valueOf(char[] data)
boolean isNull()
String toString()
int compareTo(String anotherString)


If you override method "equals()", what other function you must override for the class to work properly?
public int hashCode()
public int hash()
public static int hash()
public static int hashCode()


String objects in Java are immutable which means:
that, if constant, they cannot be changed once they are created.
that they can be changed multiple times without altering the reference.
that they can be changed one time without changing the reference.


What is the keyword to forbid the serialization of an instance field?
transient
synchronized
break
serializable
volatile


Will a program compile if the main method is defined private?
No, it does not compile
Yes, but will not run


Java's Reflection feature allows you to do things including (but not limited to) :
Optimize recursion at runtime by extending the reflection class.
Dynamically change the Java Heap Size.
Perform pseudo-pointer manipulations in Java.
Obtain the names of a class' members and display them at runtime.


What is the difference between Vector and ArrayList?
ArrayList is synchronized whereas Vector is not
Both are identical
Vector is synchronized whereas ArrayList is not


Which is a valid keyword in Java?
Float
interface
unsigned
string


The @Override annotation
All of these answers are correct
Is not required to implement an interface method.
Is not required to override an inherited method in a parent class.
Will warn you on compilation if your annotated method signature doesn't match a method in a parent class or interface.
Clearly documents the intention to override a method in a parent class or implement a method declared in an interface.


The foreach loop in Java is constructed as:
for (Object o in collection)
foreach (Object o : collection)
foreach (collection as Object o)
there is no foreach loop in Java
for (Object o : collection)


Is it possible to create zero length arrays?
Yes, but only for primitive datatypes
Yes, you can create arrays of any type with length zero
No, you cannot create zero length arrays, but the main method may be passed an array of String references that is of length zero if a program is started without any arguments
Yes, but only for arrays of object references
No, arrays of length zero do not exist in Java


Which of these is the wildcard symbol for use in generic type specification?
!
%
&
?


If you set one object variable equal to another object variable:
you end up with two copies of the data and two references to the variable.
you end up with one copy of the data and two references to the data.
you end up with one copy of the data and one reference to the data.


SWING Toolkit contains
component set (subclasses of JComponent),support classes,interfaces
support classes,interfaces
interfaces,component set (subclasses of JComponent)
component set (subclasses of JComponent)


In Math and other java.lang Classes, generally all methods are declared _.
final
static
package private
private
abstract


How do we compare enum types in java
Equals Method
Both
Arithmetic comparator "=="


what are the parts of JNDI architecture
Java API
JNDI API and JNDI SPI
JNDI API
JNDI SPI


Which of the following is true for interface variables.
They cannot exist and the compiler will throw a 'field name is ambiguous' error if you attempt to make them.
They may exist, and they can be transient and volatile.
They may exist, and they can be transient but not volatile.
They may exist, but they must be public, static and final.
They may exist, and they can be volatile but not transient.


Which of the following is not a legal identifier?
$cash
_class
m1g
31days


A call to System.gc() does what?
Grants control of the System object to the currently executing thread.
Forces the JVM to run garbage collection to reclaim memory.
Suggests that the JVM run garbage collection to reclaim memory.


find the correct output: StringBuffer fb= new StringBuffer("one two one"); int i, j ; i= fb.indexOf("one"); System.out.println(i); j= fb.LastIndexOf("one"); System.out.println(j);
1,8
0,3
1,3
0, 8


Is "main" a keyword in Java?
Yes
No


Which method is used to sort a Collection by natural order of its elements?
Sort.sort
Collections.sort
Collection.sort
CollectionsUtils.sortCollection


Can a non-generic class have a generic constructor?
Yes
No


What does a synchronized method use as a mutex in Java?
The owning object's (this's) mutex.
The method's mutex.
A globally declared mutex.


The Java Virtual Machine manages its own:
memory and allocates it as necessary.
both of these
namespace and allocates more if necessary.
none of these


Which exception could be thrown if x is a String variable? while (x.equals("apple")) {
java.lang.ClassNotFoundException
java.lang.NoSuchMethodException
None of these exceptions can be thrown.
java.lang.NullPointerException


Which of the following IS NOT a property of the equals() method?
reflexive
transitive
symmetric
atomic


Are static fields of a class included in serialization?
No
Yes


Can a HashMap contain a null key?
No
Yes


What is an abstract class?
A class with an undefined constructor
A class that is defined by another class
A class of methods that must be implemented
A class that does not define all of its methods


Non-static attributes can be accessed without an instance of the class.
True
False
Only if they are public
Only if they are private


What is the default scope of a method?
protected
package-private
public
private
static


What is the assignment of 'animal' an example of in the following code? public abstract class Animal{...} public class Dog extends Animal{...} Animal animal = new Dog();
Polymorphism
Inheritance
Encapsulation
Abstraction
Typecasting


Which of these keywords is used to manually clean up memory in java?
finalizeGarbageCollection
finalize
final
finally


If you need to determine exactly which class your object is:
use the myClass property.
use the instanceOf operator.
use the getClass() method.


Which of the following *classes* include the getSession method used to retrieve an object that implements the HttpSession interface?
HttpServletRequest
HttpServletResponse
SessionConfig
Session Context


When is an object's finalize method called?
Whenever the JVM's garbage collection algorithm decides to call it.
When no references to the object exist in the application.
When System.gc() is called.
When the object needs to release any resources it holds.


What is one of the benefits of Generics in Java?
Enforcement of better Casting at Complie time
Easy handling of ClassCastException at runtime
Improved Runtime type checking
Elimination of Casts when getting objects from Collections


Which of the following is false regarding a class of a JavaBeans component?
it is serializable.
it is a public class
it has a public constructor with no arguments
it is transient


package test; public class Test { } -------- package test.subtest; public class SubTest extends Test{} Is this code compiles without error?
No
Yes


Which method is used to force one thread to wait for another thread to finish?
sleep(long milliseconds)
stop()
yield()
join()


which of the following can cause serious system failures??
sleep()
stop()
resume()
suspend()


Which of the following APIs is used to create secure socket connections and manage digital certificates?
JSSE
Servlet
JTAPI
JNDI


Which of the following can be abstract?
All of these
Private Methods
Static Methods
Constructors
None of these


Which of these statements is correct?
new and delete are keywords in the Java language
for, while and next are keywords in the Java language
return, goto and default are keywords in the Java language
try, catch and copy are keywords in the Java language


Does Java provide any construct to find out the size of an object?
Yes, the sizeof operator
No


The keyword 'volatile' on a field is used in Java to:
Make the compiler aware that a variable will change frequently at runtime and allow the compiler to optimize for this.
Guarantee that the field's current value is read, not a thread-cached value.
Allow access to memory mapped devices (memory mapped I/O).


Which of the following variable declarations is illegal in Java?
float myVar = 5.7f;
List<int> myVar;
List<HashMap<String,Integer>> myVar;
Double[] myVar = {1.0,2.0,2.5,2.7};


What is the difference between static inner class and a non static inner class?
A static inner class can only have static methods, an inner class may have non static methods.
A static inner class has no difference from a non static inner class.
An inner class has no reference to its parent class, a static inner class does.
A static inner class has no reference to its parent class, a non static inner class does.


Which JVM parameter is used to set the maximum heap memory size?
XX:PermGemSize
Xxx
Xms
Xmx


Which java class provides variables local to each thread?
Runnable
LocalThread
ThreadLocal
Thread


String x = "abc"; In this code, abc is:
an Immutable String Object
a Mutable String Object
an Immutable String Literal
a Mutable String Literal


Which of the following is true about this Java snippet: String a = "hello"; String b = "hello"; boolean x = (a == b);
x is never true because you are comparing two different Objects.
x is true because the String values are different.
x can be true because of Java String interning.
An exception is thrown because you cannot compare Strings this way.


How many objects are created: String s1="String"; String s2="String"; String s3="String";
One
Two
Three


If I write System.exit (0); at the end of the try block, will the finally block still execute?
Yes
No


An Enum implicitly implements which of the following interfaces?
Observer and Listener
Set and Comparable
Cloneable and Serializable
Comparable and Serializable
Iterable and Set


A java.util.ConcurrentModificationException can be thrown in a mono-threaded application.
True
False


boolean b = 1 > 0 ? 1 < 0 : false; What is the value of b?
The code will not compile.
true
false


What are the minimum and maximum values of a byte?
-128 and 127
-8 and 7
This depends on the Java Virtual Machine implementation.
-255 and 256
-127 and 128


Which of the following statements are true?
(1 >>> 1) == Integer.MAX_VALUE
(-1 >> 1) == Integer.MAX_VALUE
(-1 >>> 1) == Integer.MAX_VALUE
(1 << 31) == Integer.MAX_VALUE
(1 <<< 31) == Integer.MAX_VALUE


Which of the following statements is true?
(-1 >>> 1) == Integer.MAX_VALUE
(1 << 31) == Integer.MAX_VALUE
(-1 >> 1) == Integer.MAX_VALUE
(1 >>> 1) == Integer.MAX_VALUE


What is the result when you compile and run the following code? public class Test { public void method() { for(int i = 0; i < 3; i++) { System.out.print(i); } System.out.print(i); } }
0123
None of these
Compilation error
0122


Java is a pure object oriented language. true or false?
false
true


Which one of the following statements is false?
An abstract class may implement an interface without defining any of its methods.
An abstract class may have a no-argument constructor.
An abstract class cannot implement an interface.
You can have member variables in an abstract class.


If x is a byte and y is a double, what is an acceptable type for variable z in this expression? z = (short) x/y * 2;
Short
Int
Double
Byte
Long


What's the worst-case complexity of the function Arrays.sort(int[])?
O(n)
O(n^2)
O(2^n)
O(n*log(n))


During execution of code inside a "synchronized" statement, threads other than the executing one are prevented from:
Acquiring any locks currently held by the executing thread
Making progress until the executing thread exits the block
Acquiring the built-in lock associated with the object referenced by the synchronized statement
Accessing members of the object referenced by the synchronized statement


How many bytes are in a long in Java?
32
16
8
4
2


A nested class declared inside a block (a local class) can access other variables defined in its immediately enclosing scope, but only when they are:
public
primitives
final
initialized
declared before the class


Which of the following is true about overloading vs overriding methods?
Overloaded methods must be the same data type
Final methods can be overriden, but not overloaded
Overloading arbitrarily changes method access
Overloading happens at compile time


In Java, "const" is:
not a java keyword
a regular java keyword
a reserved but unused keyword


Which of the following lines will not throw a compile time error?
int a2[5];
All throw compile time errors.
int []a1[] = new int[3][3];
int a2[4] = {3,4,5,6};


What is the difference between an inner class and a nested class?
A nested class is any class that is defined within another class. An inner class is a static nested class.
An inner class is any class that is defined within another class. A nested class is an abstract inner class.
A nested class is any class that is defined within another class. An inner class is a non-static nested class.
There is no difference; they are synonymous.


A subclass's constructor will always implicitly call its superclass's default, no-argument constructor except when:
The subclass constructor in question makes an explicit call to another of its superclass's constructors.
The subclass defines additional constructors to its default, no-argument constructor.
The superclass is abstract.
The superclass defines additional constructors to its default, no-argument constructor.


Can you overload a static method signature?
No
Yes


By which method does Java pass data?
Both pass by reference and pass by value.
Pass by reference only.
Pass by value only.


Can a constructor be final?
Yes
No


What will be the output of following Java code: int someVariable = 10_000; int someAnotherVar = 10000; if(someVariable == 10000){ System.out.println("equal"); } else{ System.out.println("not equal"); }
Runs successfully and prints "not equal"
Compile time error
Run time error
Runs successfully and prints "equal"


When using swing, which of the following is NOT a method on a JCheckBox object?
checkb.addListener(Listener);
checkb.addItemListener(item-listener);
checkb.isSelected();
checkb.setSelected(state);


Of the following, which is not a java.lang Class?
StringBuffer
Math
StringBuilder
Void
Arrays


True or false? StringBuilder is Thread-safe.
True
False


What is the output of the below code ? int a = 0; int b = 0; if (a++ == 1 && b++ == 1); System.out.println(a + " " + b);
0 1
1 1
1 0
0 0


such construct in Java: class Foo { { // some code } }
is another way to define the constructor
is an instance initializer, additional to constructor and called after it
is a class initializer, for a static fields initialization
is not proper, doesn't exist in Java
is an instance initializer, additional to constructor and called before it


Is it possible to start a thread twice?
No
Yes


byte a = 64; byte b = (byte) (a << 2); What is the value of b?
64
256
0
128
-1


Add this annotation to your annotation declaration in order to ensure it's available for reflection.
@Runtime
@Target("RUNTIME")
@Retention(RetentionPolicy.REFLECTION)
@Reflectable
@Retention(RetentionPolicy.RUNTIME)


The default constructor of an enum type is implicitly:
private
protected
public


public @interface A { String value(); } How would you change the "value" element declaration to give it an empty String as its default?
String value() default "";
String value("");
String value() = "";
String value() {return "";};
String value(default="");


Which of these statements is TRUE for enums:
All of the above.
Enum can extend another enum.
Enum can implement an interface.
Enum can extend a class.

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