Q - Given an object named obj that has a
public instance method named myMethod(), provide a
code fragment that shows the proper syntax
for accessing the method.
A - The proper syntax for accessing an
instance method named myMethod() follows:
obj.myMethod()
Q - The object-oriented approach normally
recommends hiding instance variables behind access
methods: True or False? If true, explain
why.
A - True. The object-oriented approach
normally recommends hiding instance variables behind access methods. There are
a variety of reasons why. One important reason is that hiding the instance
variables makes it possible to later modify the implementation of instance
variables to improve the behavior of objects of the class, without a
requirement for modifying code that uses the clsss, provided that the access
methods are not modified.
Q - The returning of memory (to the
operating system) occupied by objects that are no longer
needed is automatically accomplished in
Java by a feature commonly known as the
____________________.
A - The returning of memory to the
operating system is taken care of automatically by a feature of Java known as the
garbage collector.
Q - All necessary cleanup in a Java program
is performed automatically by the garbage collector:
True or False? If false, explain why.
A - False. Java does not support anything
like a destructor that is guaranteed to be called whenever the object is no
longer needed. Therefore, other than returning allocated memory, it is the
responsibility of the programmer to explicitly perform any other required
cleanup at the appropriate point in time.
Q - When does an object become eligible for
garbage collection?
A - An object becomes eligible for garbage
collection when there are no more references to that object.
Q - What can your program do to purposely
make an object eligible for garbage collection.
A - Your program can make an object
eligible for garbage collection by assigning null to all references to the
object.
Q - The purpose of garbage collection in
Java is to perform all necessary cleanup and the memory
occupied by objects that are no longer
needed will always be reclaimed by the garbage collector:
True or False? If false, explain why.
A - False. The sole purpose of garbage
collection is to reclaim memory occupied by objects that are no longer needed,
and it has no other purpose relative to necessary cleanup. An object becomes
eligible for garbage collection when there are no more references to that
object. However, just because an object is eligible for garbage collection
doesn't mean that it will be reclaimed. The garbage collector runs in a
low-priority thread, and may not run at all unless a memory shortage is
detected.
Q - Before the garbage collector reclaims
the memory occupied by an object, it always calls the
object's _________ method. (Provide the
name of the method.) Explain why this method is one of
the methods in all new classes that you
define.
A - Before the garbage collector reclaims
the memory occupied by an object, it calls the object's finalizemethod. The
finalize method is a member of the Object class. Since all classes inherit from
the Object class, your classes also contain the default finalize method.
Q - What must you do to make effective use
of the finalize method? Explain why you might want to
do this.
A - In order to make use of the finalize
method, you must override it, providing the code that you want to have executed
before the memory is reclaimed.
Q - You can always be confident that the
finalize method will be promptly executed to perform
necessary cleanup in a Java program when an
object becomes eligible for garbage collection: True
or False? If false, explain why.
A - False. Although you can be confident
that the finalize method will be called before the garbage collector reclaims
the memory occupied by a particular object, you cannot be certain when, or if
that memory will be reclaimed. There is no guarantee that the memory will be
reclaimed by the garbage collector during the execution of your program.
Q - Provide a code fragment illustrating
the method call that you can make to ask the garbage
collector to run. This guarantees that
garbage collection will take place: True or False? If false,
explain why.
A - False. Campione and Walrath indicate
that you can ask the garbage collector to run at any time by calling the method
shown below. They further point out, however, that making the request does not
guarantee that your objects will be reclaimed through garbage collection. System.gc();
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<br><font size=-1>
Interview Questions on JavaWhat if the main method is declared as private?
<br
/><font size=-1>
The program compiles properly but at runtime it will give
“Main method not public.” message.What is meant by pass by reference and pass by value in Java? Pass by reference means, passing the address itself rather than passing the value. Pass by value means passing a copy of the value. If you’re overriding the method equals() of an object, which other method you might also consider? hashCode() What is Byte Code? Or What gives java it’s “write once and run anywhere” nature? All Java programs are compiled into class files that contain bytecodes. These byte codes can be run in any platform and hence java is said to be platform independent. Expain the reason for each keyword of public static void main(String args[])? public- main(..) is the first method called by java environment when a program is executed so it has to accessible from java environment. Hence the access specifier has to be public. static: Java environment should be able to call this method without creating an instance of the class , so this method must be declared as static. void: main does not return anything so the return type must be void The argument String indicates the argument type which is given at the command line and arg is an array for string given during command line. What are the differences between == and .equals() ? Or what is difference between == and equals Or Difference between == and equals method Or What would you use to compare two String variables - the operator == or the method equals()? Or How is it possible for two String objects with identical values not to be equal under the == operator? The == operator compares two objects to determine if they are the same object in memory i.e. present in the same memory location. It is possible for two String objects to have the same value, but located in different areas of memory. == compares references while .equals compares contents. The method public boolean equals(Object obj) is provided by the Object class and can be overridden. The default implementation returns true only if the object is compared with itself, which is equivalent to the equality operator == being used to compare aliases to the object. String, BitSet, Date, and File override the equals() method. For two String objects, value equality means that they contain the same character sequence. For the Wrapper classes, value equality means that the primitive values are equal.
== comparison : true == comparison : true Using equals method : true false Using equals method : true What if the static modifier is removed from the signature of the main method? Or What if I do not provide the String array as the argument to the method? Program compiles. But at runtime throws an error “NoSuchMethodError”. Why oracle Type 4 driver is named as oracle thin driver? Oracle provides a Type 4 JDBC driver, referred to as the Oracle “thin” driver. This driver includes its own implementation of a TCP/IP version of Oracle’s Net8 written entirely in Java, so it is platform independent, can be downloaded to a browser at runtime, and does not require any Oracle software on the client side. This driver requires a TCP/IP listener on the server side, and the client connection string uses the TCP/IP port address, not the TNSNAMES entry for the database name. What is the difference between final, finally and finalize? What do you understand by the java final keyword? Or What is final, finalize() and finally? Or What is finalize() method? Or What is the difference between final, finally and finalize? Or What does it mean that a class or member is final? o final - declare constant o finally - handles exception o finalize - helps in garbage collection Variables defined in an interface are implicitly final. A final class can’t be extended i.e., final class may not be subclassed. This is done for security reasons with basic classes like String and Integer. It also allows the compiler to make some optimizations, and makes thread safety a little easier to achieve. A final method can’t be overridden when its class is inherited. You can’t change value of a final variable (is a constant). finalize() method is used just before an object is destroyed and garbage collected. finally, a key word used in exception handling and will be executed whether or not an exception is thrown. For example, closing of open connections is done in the finally method. What is the Java API? The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets. What is the GregorianCalendar class? The GregorianCalendar provides support for traditional Western calendars. What is the ResourceBundle class? The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program’s appearance to the particular locale in which it is being run. Why there are no global variables in Java? Global variables are globally accessible. Java does not support globally accessible variables due to following reasons:
The valueOf() function of Integer class is is used to convert string to Number. Here is the code example: String numString = “1000″; int id=Integer.valueOf(numString).intValue(); What is the SimpleTimeZone class? The SimpleTimeZone class provides support for a Gregorian calendar. What is the difference between a while statement and a do statement? A while statement (pre test) checks at the beginning of a loop to see whether the next loop iteration should occur. A do while statement (post test) checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the loop body at least once. What is the Locale class? The Locale class is used to tailor a program output to the conventions of a particular geographic, political, or cultural region. Describe the principles of OOPS. There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation. Explain the Inheritance principle. Inheritance is the process by which one object acquires the properties of another object. Inheritance allows well-tested procedures to be reused and enables changes to make once and have effect in all relevant places What is implicit casting? Implicit casting is the process of simply assigning one entity to another without any transformation guidance to the compiler. This type of casting is not permitted in all kinds of transformations and may not work for all scenarios.
Example
int i = 1000;long j = i; //Implicit casting Is sizeof a keyword in java? The sizeof operator is not a keyword. What is a native method? A native method is a method that is implemented in a language other than Java. In System.out.println(), what is System, out and println? System is a predefined final class, out is a PrintStream object and println is a built-in overloaded method in the out object. What are Encapsulation, Inheritance and Polymorphism Or Explain the Polymorphism principle. Explain the different forms of Polymorphism. Polymorphism in simple terms means one name many forms. Polymorphism enables one entity to be used as a general category for different types of actions. The specific action is determined by the exact nature of the situation. Polymorphism exists in three distinct forms in Java: • Method overloading • Method overriding through inheritance • Method overriding through the Java interface What is explicit casting? Explicit casting in the process in which the complier are specifically informed to about transforming the object.
Example
long i = 700.20;int j = (int) i; //Explicit casting What is the Java Virtual Machine (JVM)? The Java Virtual Machine is software that can be ported onto various hardware-based platforms What do you understand by downcasting? The process of Downcasting refers to the casting from a general to a more specific type, i.e. casting down the hierarchy What are Java Access Specifiers? Or What is the difference between public, private, protected and default Access Specifiers? Or What are different types of access modifiers? Access specifiers are keywords that determine the type of access to the member of a class. These keywords are for allowing privileges to parts of a program such as functions and variables. These are: • Public : accessible to all classes • Protected : accessible to the classes within the same package and any subclasses. • Private : accessible only to the class to which they belong • Default : accessible to the class to which they belong and to subclasses within the same package Which class is the superclass of every class? Object. Name primitive Java types. The 8 primitive types are byte, char, short, int, long, float, double, and boolean. What is the difference between static and non-static variables? Or What are class variables? Or What is static in java? Or What is a static method? A static variable is associated with the class as a whole rather than with specific instances of a class. Each object will share a common copy of the static variables i.e. there is only one copy per class, no matter how many objects are created from it. Class variables or static variables are declared with the static keyword in a class. These are declared outside a class and stored in static memory. Class variables are mostly used for constants. Static variables are always called by the class name. This variable is created when the program starts and gets destroyed when the programs stops. The scope of the class variable is same an instance variable. Its initial value is same as instance variable and gets a default value when its not initialized corresponding to the data type. Similarly, a static method is a method that belongs to the class rather than any object of the class and doesn’t apply to an object or even require that any objects of the class have been instantiated. Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can’t override a static method with a non-static method. In other words, you can’t change a static method into an instance method in a subclass. Non-static variables take on unique values with each object instance. What is the difference between the boolean & operator and the && operator? If an expression involving the boolean & operator is evaluated, both operands are evaluated, whereas the && operator is a short cut operator. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. If the first operand evaluates to false, the evaluation of the second operand is skipped. How does Java handle integer overflows and underflows? It uses those low order bytes of the result that can fit into the size of the type allowed by the operation. What if I write static public void instead of public static void? Program compiles and runs properly. What is the difference between declaring a variable and defining a variable? In declaration we only mention the type of the variable and its name without initializing it. Defining means declaration + initialization. E.g. String s; is just a declaration while String s = new String (”bob”); Or String s = “bob”; are both definitions. What type of parameter passing does Java support? In Java the arguments (primitives and objects) are always passed by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object. Explain the Encapsulation principle. Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. Objects allow procedures to be encapsulated with their data to reduce potential interference. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by other code defined outside the wrapper. What do you understand by a variable? Variable is a named memory location that can be easily referred in the program. The variable is used to hold the data and it can be changed during the course of the execution of the program. What do you understand by numeric promotion? The Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integral and floating-point operations may take place. In the numerical promotion process the byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required. What do you understand by casting in java language? What are the types of casting? The process of converting one data type to another is called Casting. There are two types of casting in Java; these are implicit casting and explicit casting. What is the first argument of the String array in main method? The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name. If we do not provide any arguments on the command line, then the String array of main method will be empty but not null. How can one prove that the array is not null but empty? Print array.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print array.length. Can an application have multiple classes having main method? Yes. While starting the application we mention the class name to be run. The JVM will look for the main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main method. When is static variable loaded? Is it at compile time or runtime? When exactly a static block is loaded in Java? Static variable are loaded when classloader brings the class to the JVM. It is not necessary that an object has to be created. Static variables will be allocated memory space when they have been loaded. The code in a static block is loaded/executed only once i.e. when the class is first initialized. A class can have any number of static blocks. Static block is not member of a class, they do not have a return statement and they cannot be called directly. Cannot contain this or super. They are primarily used to initialize static fields. Can I have multiple main methods in the same class? We can have multiple overloaded main methods but there can be only one main method with the following signature : public static void main(String[] args) {} No the program fails to compile. The compiler says that the main method is already defined in the class. Explain working of Java Virtual Machine (JVM)? JVM is an abstract computing machine like any other real computing machine which first converts .java file into .class file by using Compiler (.class is nothing but byte code file.) and Interpreter reads byte codes. How can I swap two variables without using a third variable? Add two variables and assign the value into First variable. Subtract the Second value with the result Value. and assign to Second variable. Subtract the Result of First Variable With Result of Second Variable and Assign to First Variable. Example: int a=5,b=10;a=a+b; b=a-b; a=a-b; An other approach to the same question You use an XOR swap. for example: int a = 5; int b = 10; a = a ^ b; b = a ^ b; a = a ^ b; What is data encapsulation? Encapsulation may be used by creating ‘get’ and ’set’ methods in a class (JAVABEAN) which are used to access the fields of the object. Typically the fields are made private while the get and set methods are public. Encapsulation can be used to validate the data that is to be stored, to do calculations on data that is stored in a field or fields, or for use in introspection (often the case when using javabeans in Struts, for instance). Wrapping of data and function into a single unit is called as data encapsulation. Encapsulation is nothing but wrapping up the data and associated methods into a single unit in such a way that data can be accessed with the help of associated methods. Encapsulation provides data security. It is nothing but data hiding. What is reflection API? How are they implemented? Reflection is the process of introspecting the features and state of a class at runtime and dynamically manipulate at run time. This is supported using Reflection API with built-in classes like Class, Method, Fields, Constructors etc. Example: Using Java Reflection API we can get the class name, by using the getName method. Does JVM maintain a cache by itself? Does the JVM allocate objects in heap? Is this the OS heap or the heap maintained by the JVM? Why Yes, the JVM maintains a cache by itself. It creates the Objects on the HEAP, but references to those objects are on the STACK. What is phantom memory? Phantom memory is false memory. Memory that does not exist in reality. Can a method be static and synchronized? A static method can be synchronized. If you do so, the JVM will obtain a lock on the java.lang. Class instance associated with the object. It is similar to saying: synchronized(XYZ.class) { } What is difference between String and StringTokenizer? A StringTokenizer is utility class used to break up string.
Example:
StringTokenizer st = new StringTokenizer(”Hello World”);while (st.hasMoreTokens()) { System.out.println(st.nextToken()); }
Output:
HelloWorld
Q 1What do we call an operator that
operates on only one operand?
A - An operator that operates on only one
operand is called a unary operator.
Q 2- What do we call an operator that
operates on two operands?
A - An operator that operates on two
operands is called a binary operator.
Q 3- Is the minus sign a unary or a
binary operator, or both? Explain your answer.
A - Both. As a binary operator, the minus
sign causes its right operand to be subtracted from its left operand. As a
unary operator, the minus sign causes the algebraic sign of the right operand
to be changed.
Q 4- Describe operator overloading.
A - For those languages that support it
(such as C++) operator overloading means that the programmer can
redefine the behavior of an operator with
respect to objects of a new type defined by that program.
Q5- Java programmers may overload
operators: True or False?
A 6- False: Unfortunately, Java does not
support operator overloading.
Q7 - Show the symbols used for the
following operators in Java: assignment, not equal, addition,cast.
A - The above listed operators in order
are: = != + (type)
Q8 - Is any operator automatically
overloaded in Java? If so, identify it and describe its overloaded
behavior.
A - The plus sign (+) is automatically
overloaded in Java. The plus sign can be used to perform arithmetic
addition. It can also be used to
concatenate strings. However, the plus sign does more than concatenate
strings. It also performs a conversion to String type. When the plus sign is
used to concatenate strings, the operand on the right is automatically
converted to a character string before being concatenated with the operand on
the left. This assumes that the compiler knows enough about the operand on
the right to be able to successfully perform the conversion. It has that
knowledge for all of the primitive types and most or all of the built-in
reference types.
Q 9- What is the purpose of the cast
operator?
A - The cast operator is used to
purposely convert from one type to another.
Q10 - The increment operator is a binary
operator: True or False?
A - False: The increment operator is a
unary operator.
Q11 - Show the symbol for the increment
operator.
A - The symbol for the increment operator
is two plus signs with nothing between them (++).
Q 12- Describe the appearance and the
behavior of the increment operator with both prefix and
postfix notation. Show example, possibly
incomplete, code fragments illustrating both notational
forms.
A - The increment operator may be used
with both prefix and postfix notation. Basically, the increment operator
causes the value of the variable to which it is applied to be increased by
one. With prefix notation, the operand appears to the right of the operator (
++X), while with postfix notation, the operand appears to the left of the
operator (X++).
The difference in behavior has to do with
the point in time that the increment actually occurs if the operator and its
operand appear as part of a larger overall expression. With the prefix
version, the variable is incremented before it is used to evaluate the larger
overall expression. With the postfix version, the variable is used to
evaluate the larger overall expression and then it is incremented.
Q13 - Show the output that would be
produced by the following Java application.
class prg1 { //define the controlling class
public static void main(String[] args){ //define main method
int x = 5, X = 5, y = 5, Y = 5;
System.out.println("x = " + x );
System.out.println("X = " + X );
System.out.println("x + X++ = " + (x + X++) );
System.out.println("X = " + X );
System.out.println();
System.out.println("y = " + y );
System.out.println("Y = " + Y );
System.out.println("y + ++Y = " + (y + ++Y) );
System.out.println("Y = " + Y );
}//end main
}//End
class. Note no semicolon
required
//End Java application
A - The output from this Java application
follows:
x = 5
X = 5
x + X++ = 10
X = 6
y = 5
Y = 5
y + ++Y = 11
Y = 6
Q 14 - Binary operators use outfix
notation: True or False? If your answer is False, explain why.
A - False: Binary operators use infix
notation, which means that the operator appears between its operands.
Q15 - In practice, what does it mean to
say that an operator that has performed an action returns a
value (or evaluates to a value) of a
given type?
A - As a result of performing the
specified action, an operator can be said to return a value (or evaluate to a
value) of a given type. The type depends
on the operator and the type of the operands. To evaluate to a value means
that after the action is performed, the operator and its operands are
effectively replaced in the expression by the value that is returned.
Q 16 - What are the four categories of
operators described in Baldwin's Java tutorial on operators? Do
you agree with this categorization? If
not, explain why not.
A - Some authors divide Java's operators
into the following categories:
arithmetic
relational and conditional (typically called relational and logical in
C++)
bitwise and logical
assignment
Q17 - Show and describe at least five of
the binary arithmetic operators supported by Java
(Clarification: binary operators does not
mean bitwise operators).
A - Java support various arithmetic
operators on floating point and integer numbers. The following table lists
five of the binary arithmetic operators supported by Java.
Operator
Description
+ Adds its operands
- Subtracts the right
operand from the left operand
* Multiplies the
operands
/ Divides the left
operand by the right operand
% Remainder of dividing the left operand by
the right operand
Q18 - In addition to arithmetic addition,
what is another use for the plus operator (+)? Show an
example code fragment to illustrate your
answer. The code fragment need not be a complete
statement.
A - The plus operator (+) is also used to
concatenate strings : "IMR " + " global
Ltd."
Q19 - When the plus operator (+) is used
as a concatenation operator, what is the nature of its
behavior if its right operand is not of
type String? If the right operand is a variable that is not of type
String, what is the impact of this
behavior on that variable.
A - In this case, the operator also
coerces the value of the right operand to a string representation for use in
the expression only. If the right operand is a variable, the value stored in
the variable is not modified in any way.
Q 20- Show and describe four unary
arithmetic operators supported by Java.
A - Java supports the following four
unary arithmetic operators.
Operator
Description
+ Indicates a positive
value
- Negates, or changes
algebraic sign
++ Adds one to the
operand, both prefix and postfix
-- Subtracts one from
operand, prefix and postfix
Q20 - What is the type returned by
relational operators in Java?
A - Relational operators return the boolean
type in Java.
Q 21- Show and describe six different
relational operators supported by Java.
A - Java supports the following set of
relational operators:
Operator
Returns true if
> Left operand is
greater than right operand
>=
Left operand is greater than or equal to right operand
< Left operand is less
than right operand
<= Left operand is less
than or equal to right operand
== Left operand is equal
to right operand
!= Left operand is not
equal to right operand
Q 22- Show the output that would be
produced by the following Java application:
class prg2 { //define the controlling class
public static void main(String[] args){ //define main method
System.out.println("The relational 6<5 is " + (6<5 )
);
System.out.println("The relational 6>5 is " + (6>5 )
);
}//end main
}//End
class. Note no semicolon
required
//End Java application
A - This program produces the following
output:
The relational 6<5 is false
The relational 6>5 is true
Q23 - Show and describe three operators
(frequently referred to as conditional operators in Java and
logical operators in C++) which are often
combined with relational operators to construct more
complex expressions (often called
conditional expressions). Hint: The && operator returns true if
the left and right operands are both
true. What are the other two and how do they behave?
A - The following three logical or
conditional operators are supported by Java.
Operator Typical Use Returns true if
&& Left && Right Left and Right are both true
||
Left || Right Either Left or
Right is true
!
! Right Right is false
Q24 - Describe the special behavior of
the || operator in the following expression for the case where
the value of the variable a is less than
the value of the variable b.
(a < b) || (c < d)
A - An important characteristic of the
behavior of the && and || operators in Java is that the expressions
are
evaluated from left to right, and the
evaluation of the expression is terminated as soon as the result of
evaluating the expression can be determined. For example, in the above
expression, if the variable a is less than the variable b , there is no need
to evaluate the right operand of the || to determine the value of the entire
expression. Thus, evaluation will terminate as soon as it is determined that
a is less than b.
Q25 - Show the symbols used for the
bitwise and operator and the or operator.
A - The & operator in Java is a
bitwise and and the | operator is a bitwise or.
Q26 - The logical and operator is
represented in Java by the && symbol. What is the representation
of the bitwise and operator in Java?
A - The bitwise and operator is
represented by the & symbol in Java.
Q27 - Show and describe five operators in
Java that perform actions on the operands one bit at a time
(bitwise operators).
A - The following table shows the seven
bitwise operators supported by Java.
Operator
Typical Use Operation
>> OpLeft >> Dist Shift bits of OpLeft right by Dist bits
(signed)
<< OpLeft << Dist Shift bits of OpLeft left by Dist bits
>>> OpLeft >>> Dist Shift bits of OpLeft right by Dist bits
(unsigned)
& OpLeft & OpRight Bitwise and of the two operands
|
OpLeft | OpRight Bitwise
inclusive or of the two operands
^
OpLeft ^ OpRight Bitwise
exclusive or (xor) of the two operands
~ ~ OpRight Bitwise complement of the right
operand (unary)
Q28 - In Java, the signed right shift
operation populates the vacated bits with the zeros, while the left
shift and the unsigned right shift
populate the vacated bits with the sign bit: True or False. If your
answer is False, explain why.
A - False: In Java, the signed right
shift operation populates the vacated bits with the sign bit, while the left
shift and the unsigned right shift populate the vacated bits with zeros.
Q29 - In a signed right-shift operation
in Java, the bits shifted off the right end are lost: True or False.
If your answer is False, explain why.
A - True: For both Java and C++, bits
shifted off the right end are lost.
Q30 - Using the symbols 1 and 0 construct
a table showing the four possible combinations of 1 and 0.
Using a 1 or a 0, show the result of the
bitwise and operation on these four combinations of 1 and 0.
A - The answer is:
1 and 1 produces 1
1 and 0 produces 0
0 and 1 produces 0
0 and 0 produces 0
Q 31- Using the symbols 1 and 0 construct
a truth table showing the four possible combinations of 1
and 0. Using a 1 or a 0, show the result
of the bitwise inclusive or operation on these four
combinations on these four combinations
of 1 and 0.
A - The answer for the inclusive or is:
1 or 1 produces 1
1 or 0 produces 1
0 or 1 produces 1
0 or 0 produces 0
Q 32- Using the symbols 1 and 0 construct
a truth table showing the four possible combinations of 1
and 0. Using a 1 or a 0, show the result
of the bitwise exclusive or operation on these four
combinations on these four combinations
of 1 and 0.
A - The answer for the exclusive or is:
1 xor 1 produces 0
1 xor 0 produces 1
0 xor 1 produces 1
0 xor 0 produces 0
Q 33- For the exclusive or, if the two
bits are different, the result is a 1. If the two bits are the same,
the result is a 0. True or False? If your
answer is False, explain why.
A - True.
Q 34- Is the assignment operator a unary
operator or a binary operator. Select one or the other.
A - The assignment operator is a binary
operator.
Q 35- In Java, when using the assignment
operator, the value stored in memory and represented by the
right operand is copied into the memory
represented by the left operand: True or False? If your
answer is False, explain why.
A - True.
Q 36- Show two of the shortcut assignment
operators and explain how they behave by comparing
them with the regular (nonshortcut)
versions. Hint: The (^=) operator is a shortcut assignment
operator.
A - Java supports the following list of
shortcut assignment operators. These operators allow you to perform an
assignment and another operation with a single operator. += -= *= /= %= &= |= ^= <<=
>>= >>>=
For example, the two statements which
follow perform the same operation.
x += y; x = x + y;
The behavior of all the shortcut
assignment operators follows this same pattern.
Q 37 - Write a Java application
illustrates the difference between the
prefix and the postfix versions of the increment operator.
class prog3{
static public void main(String[] args){
int x = 3;
int y = 3;
int z = 10;
System.out.println("Prefix version gives " + (z + ++x));
System.out.println("Postfix version gives " + (z + y++));
}//end main
}//end class
Q38
Write a Java application that illustrates the use of the following
relational operators: < > <=
>= == !=
class Prog4 { //define the controlling
class
public static void main(String[] args){ //define main method
System.out.println("The relational 6<5 is " + (6<5 )
);
System.out.println("The relational 6>5 is " + (6>5 )
);
System.out.println("The relational 5>=5 is " + (5>=5 )
);
System.out.println("The relational 5<=5 is " + (5<=5 )
);
System.out.println("The relational 6==5 is " + (6==5 ) );
System.out.println("The relational 6!=5 is " + (6!=5 ) );
}//end main
}//End prog4 class. Note no semicolon required
Q39 - Write a Java application that
illustrates the use of the following logical or conditional operators:
&&
|| !
class prg5 { //define the controlling class
public static void main(String[] args){ //define main method
System.out.println("true and true is " + (true &&
true) );
System.out.println("true and false is " + (true &&
false) );
System.out.println("true or true is " + (true || true) );
System.out.println("true or false is " + (true || false) );
System.out.println("false or false is " + (false || false)
);
System.out.println("not true is " + (! true) );
System.out.println("not false is " + (! false) );
}//end main
}
Q40 - Java supports a constant type: True
or False. If false, explain why.
A - Java does not support a constant
type. However, in Java, it is possible to achieve the same result by
declaring and initializing a variable and
making it final.
Q41 Provide a code fragment that
illustrates the syntax for creating a named constant in Java.
A - The syntax for creating a named
constant in Java is as follows: final float PI = 3.14159;
Q42 - What is the common method of
controlling the order of evaluation of expressions in Java?
A -
you can control the order of evaluation by the use of parentheses.
Q43 - What are the three actions normally
involved in the operation of a loop (in addition to executing
the code in the body of the loop)?
A - The operation of a loop normally
involves the following three actions in addition to executing the code in the
body of the loop:
Initialize a control variable.
Test the control variable in a
conditional expression.
Update the control variable.
Association
Association is a relationship
between two objects. In other words, association defines the multiplicity
between objects. You may be aware of one-to-one, one-to-many, many-to-one,
many-to-many all these words define an association between objects.
Aggregation is a special form of association. Composition is a special form
of aggregation.
Example: A Student and a Faculty are having an association.
Aggregation
Aggregation is a special case
of association. A directional association between objects. When an object
‘has-a’ another object, then you have got an aggregation between them.
Direction between them specified which object contains the other object.
Aggregation is also called a “Has-a” relationship.
Composition
Composition is a special case
of aggregation. In a more specific manner, a restricted aggregation is called
composition. When an object contains the other object, if the contained
object cannot exist without the existence of container object, then it is
called composition.
Differences between stringbuffer and
strind stringbulder?
The StringBuilder class was introduced with JDK 5.0.
Essentially, a StringBuffer is a thread-safe version of StringBuilder. If you
are only adding/removing characters from a single-thread, the StringBuilder
implementation will be faster. If you are using multiple threads to add and
remove characters, use StringBuffer.
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