Packages and interface

1) What are packages ? what is use of packages ?
Ans :The package statement defines a name space in which classes are stored.If you omit the package, the classes are put into the default package.
Signature... package pkg;
Use: * It specifies to which package the classes defined in a file belongs to. * Package is both naming and a visibility control mechanism.

2) What is difference between importing "java.applet.Applet" and "java.applet.*;" ?
Ans :"java.applet.Applet" will import only the class Applet from the package java.applet
Where as "java.applet.*" will import all the classes from java.applet package.

3) What do you understand by package access specifier?
Ans : public: Anything declared as public can be accessed from anywhere
private: Anything declared in the private can’t be seen outside of its class.
default: It is visible to subclasses as well as to other classes in the same package.

4) What is interface? What is use of interface?
Ans : It is similar to class which may contain method’s signature only but not bodies.
Methods declared in interface are abstract methods. We can implement many interfaces on a class which support the multiple inheritance.

5) Is it is necessary to implement all methods in an interface?
Ans : Yes. All the methods have to be implemented.
6) Which is the default access modifier for an interface method?
Ans : public.

7) Can we define a variable in an interface ?and what type it should be ?
Ans : Yes we can define a variable in an interface. They are implicitly final and static.

8) What is difference between interface and an abstract class?
Ans : All the methods declared inside an Interface are abstract. Where as abstract class must have at least one abstract method and others may be concrete or abstract.
In Interface we need not use the keyword abstract for the methods.

9) By default, all program import the java.lang package.
True/False
Ans : True
10) Java compiler stores the .class files in the path specified in CLASSPATH
environmental variable.
True/False
Ans : False

11) User-defined package can also be imported just like the standard packages.
True/False
Ans : True

12) When a program does not want to handle exception, the ______class is used.
Ans : Throws

13) The main subclass of the Exception class is _______ class.
Ans : RuntimeException

14) Only subclasses of ______class may be caught or thrown.
Ans : Throwable

15) Any user-defined exception class is a subclass of the _____ class.
Ans : Exception

16) The catch clause of the user-defined exception class should ______ its
Base class catch clause.
Ans : Exception

17) A _______ is used to separate the hierarchy of the class while declaring an
Import statement.
Ans : Package

18) All standard classes of Java are included within a package called _____.
Ans : java.lang

19) All the classes in a package can be simultaneously imported using ____.
Ans : *

20) Can you define a variable inside an Interface. If no, why? If yes, how?
Ans.: YES. final and static

Introduction to Classes and Methods

1) Which is used to get the value of the instance variables?
Ans: Dot notation.

2) The new operator creates a single instance named class and returns a
reference to that object.
a)True
b)False
Ans: a.

3) A class is a template for multiple objects with similar features.
a)True
b)False
Ans: a.

4) What is mean by garbage collection?
Ans: When an object is no longer referred to by any variable, Java automatically
reclaims memory used by that object. This is known as garbage collection.

5) What are methods and how are they defined?
Ans: Methods are functions that operate on instances of classes in which they are defined.Objects can communicate with each other using methods and can call methods in other classes.
Method definition has four parts. They are name of the method, type of object or primitive type the method returns, a list of parameters and the body of the method.
A method's signature is a combination of the first three parts mentioned above.

6) What is calling method?
Ans: Calling methods are similar to calling or referring to an instance variable. These methods are accessed using dot notation.
Ex: obj.methodname(param1,param2)

7) Which method is used to determine the class of an object?
Ans: getClass( ) method can be used to find out what class the belongs to. This class is defined in the object class and is available to all objects.

8) All the classes in java.lang package are automatically imported when
a program is compiled.
a)True
b)False
Ans: a.

9) How can class be imported to a program?
Ans: To import a class, the import keyword should be used as shown.;
import classname;

10) How can class be imported from a package to a program?
Ans: import java . packagename . classname (or) import java.package name.*;

11) What is a constructor?
Ans: A constructor is a special kind of method that determines how an object is
initialized when created.


12) Which keyword is used to create an instance of a class?
Ans: new.

13) Which method is used to garbage collect an object?
Ans: finalize ().

14) Constructors can be overloaded like regular methods.
a)True
b)False
Ans: a.

15) What is casting?
Ans: Casting is bused to convert the value of one type to another.

16) Casting between primitive types allows conversion of one primitive type to another.
a)True
b)False
Ans: a.

17) Casting occurs commonly between numeric types.
a)True
b)False
Ans: a.

18) Boolean values can be cast into any other primitive type.
a)True
b)False
Ans: b.

19) Casting does not affect the original object or value.
a)True
b)False
Ans: a.

20) Which cast must be used to convert a larger value into a smaller one?
Ans: Explicit cast.

21) Which cast must be used to cast an object to another class?
Ans: Specific cast.

22) Which of the following features are common to both Java & C++?
A.The class declaration
b.The access modifiers
c.The encapsulation of data & methods with in objects
d.The use of pointers
Ans: a,b,c.

23) Which of the following statements accurately describe the use of access modifiers within a class definition?
a.They can be applied to both data & methods
b.They must precede a class's data variables or methods
c.They can follow a class's data variables or methods
d.They can appear in any order
e.They must be applied to data variables first and then to methods
Ans: a,b,d.
24) Suppose a given instance variable has been declared private.
Can this instance variable be manipulated by methods out side its class?
a.yes
b.no
Ans: b.

25) Which of the following statements can be used to describe a public method?
a.It is accessible to all other classes in the hierarchy
b.It is accessablde only to subclasses of its parent class
c.It represents the public interface of its class
d.The only way to gain access to this method is by calling one of the public class
methods
Ans: a,c.

26) Which of the following types of class members can be part of the internal part of a class?
a.Public instance variables
b.Private instance variables
c.Public methods
d.Private methods
Ans: b,d.

27) You would use the ____ operator to create a single instance of a named class.
a.new
b.dot
Ans: a.

28) Which of the following statements correctly describes the relation between an object and the instance variable it stores?
a.Each new object has its own distinctive set of instance variables
b.Each object has a copy of the instance variables of its class
c.the instance variable of each object are seperate from the variables of other objects
d.The instance variables of each object are stored together with the variables of other objects
Ans: a,b,c.

29) If no input parameters are specified in a method declaration then the declaration will include __.
a.an empty set of parantheses
b.the term void
Ans: a.

APTITUDE PART

(1)A man bought two horses for Rs.924 each and sold one horse for 15% profit and the other for 15% loss.What is the net gain?
(2) Two pumps fill atank in 20 hrs. One pump fills the same tank 10hrs. faster than the other pump. In what time the other pump fills
the tank?
(3) X men in Xhrs/day finish a work in x days. Y men in y hours per day finish the work in
(a) X**2/Y**2 (b)X**3/Y**2 (c) Y**2/X**2 (d) Y**3/X**2
(4) 8 men + 2 boys finish a work in 16 days. 2 men + 5 boys finish a work in 20 days. 8 men and 8 boys finish the same work in how
many days?
(5)A & B are two trains, travell from X & Y stations to Y & X stations after crossing each other A takes 4 hrs.48 mins. To reach Y
station. B takes 3hrs.20 mins. to reach X station. The speed A is 45kmph. Speed of B is ?
(6) 5 questions on series
(a) ab--bbc---ac----accc
(b) &(c) like this 5.
(7)5 questions on alfabets.
(8) 10 questions on English Grammer.
(9) 20 questions on reasoning.

DE Shaw

Write the programs for the following problems in C.

1. Swap two variables x,y without using a temporary variable.


2. Write algorithm for finding the GCD of a number.


3.Write a program for reversing the given string.


4. The integers from 1 to n are stored in an array in a random
fashion. but one integer is missing. Write a program to find the
missing integer.

Ans): Hint : The sum of n natural numbers is = n(n+1)/2.
if we subtract the above sum from the sum of all the
numbers in the array , the result is nothing but the
missing number.


5. Some bit type of questions has been given on pointers asking to
to find whether it is correct from syntax point of view. and if
it is correct explain what it will do. (around 15 bits).


Section-B


6. For the following C program

#define AND &&
#define ARRANGE (a>25 AND a<50)
main()
{int a = 30;
if (ARRANGE)
printf("within range");
else
printf("out of range");
}

What is the output?


7. For the following C program

#define AREA(x)(3.14*x*x)
main()
{float r1=6.25,r2=2.5,a;
a=AREA(r1);
printf("\n Area of the circle is %f", a);
a=AREA(r2);
printf("\n Area of the circle is %f", a);
}

What is the output?

Ans. Area of the circle is 122.656250
Area of the circle is 19.625000


8. What do the following statements indicate. Explain.

int(*p)[10]

int*f()

int(*pf)()

int*p[10]

Refer to:
-- Kernighan & Ritchie page no. 122
-- Schaum series page no. 323


9. Write a C program to find whether a stack is progressing in forward
or reverse direction.


10. Write a C program that reverses the linked list.

JAVA-Control Statements

1) What are the programming constructs?
Ans: a) Sequential
b) Selection -- if and switch statements
c) Iteration -- for loop, while loop and do-while loop

2) class conditional {
public static void main(String args[]) {
int i = 20;
int j = 55;
int z = 0;
z = i < j ? i : j; // ternary operator
System.out.println("The value assigned is " + z);
}
}
What is output of the above program?
Ans: The value assigned is 20

3) The switch statement does not require a break.
a)True
b)False
Ans: b.

4) The conditional operator is otherwise known as the ternary operator.
a)True
b)False
Ans: a.

5) The while loop repeats a set of code while the condition is false.
a)True
b)False
Ans: b.

6) The do-while loop repeats a set of code atleast once before the condition is tested.
a)True
b)False
Ans: a.

7) What are difference between break and continue?
Ans: The break keyword halts the execution of the current loop and forces control out of the loop.
The continue is similar to break, except that instead of halting the execution of the loop, it starts the next iteration.

8) The for loop repeats a set of statements a certain number of times until a condition is matched.
a)True
b)False
Ans: a.

9) Can a for statement loop indefintely?
Ans : Yes.

10) What is the difference between while statement and a do statement/
Ans : A while statement checks at the beginning of a loop to see whether the next loop iteration should occur.
A do statement 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 body of a loop at least once.

Operators

1) What are operators and what are the various types of operators available in Java?
Ans: Operators are special symbols used in expressions.
The following are the types of operators:
Arithmetic operators,
Assignment operators,
Increment & Decrement operators,
Logical operators,
Biwise operators,
Comparison/Relational operators and
Conditional operators

2) The ++ operator is used for incrementing and the -- operator is used for
decrementing.
a)True
b)False
Ans: a.

3) Comparison/Logical operators are used for testing and magnitude.
a)True
b)False
Ans: a.

4) Character literals are stored as unicode characters.
a)True
b)False
Ans: a.

5) What are the Logical operators?
Ans: OR(|), AND(&), XOR(^) AND NOT(~).

6) What is the % operator?
Ans : % operator is the modulo operator or reminder operator. It returns the reminder of dividing the first operand by second operand.
7) What is the value of 111 % 13?
3
5
7
9
Ans : c.

8) Is &&= a valid operator?
Ans : No.

9) Can a double value be cast to a byte?
Ans : Yes

10) Can a byte object be cast to a double value ?
Ans : No. An object cannot be cast to a primitive value.

11) What are order of precedence and associativity?
Ans : Order of precedence the order in which operators are evaluated in expressions.
Associativity determines whether an expression is evaluated left-right or right-left.

12) Which Java operator is right associativity?
Ans : = operator.

13) What is the difference between prefix and postfix of -- and ++ operators?
Ans : The prefix form returns the increment or decrement operation and returns the value of the increment or decrement operation.
The postfix form returns the current value of all of the expression and then
performs the increment or decrement operation on that value.

14) What is the result of expression 5.45 + "3,2"?
The double value 8.6
The string ""8.6"
The long value 8.
The String "5.453.2"
Ans : d

15) What are the values of x and y ?
x = 5; y = ++x;
Ans : x = 6; y = 6

16) What are the values of x and z?
x = 5; z = x++;
Ans : x = 6; z = 5

JAVA-Data types,variables and Arrays

1) What is meant by variable?
Ans: Variables are locations in memory that can hold values. Before assigning any value to a variable, it must be declared.

2) What are the kinds of variables in Java? What are their uses?
Ans: Java has three kinds of variables namely, the instance variable, the local variable and the class variable.
Local variables are used inside blocks as counters or in methods as temporary variables and are used to store information needed by a single method.
Instance variables are used to define attributes or the state of a particular object and are used to store information needed by multiple methods in the objects.
Class variables are global to a class and to all the instances of the class and are useful for communicating between different objects of all the same class or keeping track of global states.

3) How are the variables declared?
Ans: Variables can be declared anywhere in the method definition and can be initialized during their declaration.They are commonly declared before usage at the beginning of the definition.
Variables with the same data type can be declared together. Local variables must be given a value before usage.

4) What are variable types?
Ans: Variable types can be any data type that java supports, which includes the eight primitive data types, the name of a class or interface and an array.

5) How do you assign values to variables?
Ans: Values are assigned to variables using the assignment operator =.

6) What is a literal? How many types of literals are there?
Ans: A literal represents a value of a certain type where the type describes how that value behaves.
There are different types of literals namely number literals, character literals,
boolean literals, string literals,etc.

7) What is an array?
Ans: An array is an object that stores a list of items.

8) How do you declare an array?
Ans: Array variable indicates the type of object that the array holds.
Ex: int arr[];

9) Java supports multidimensional arrays.
a)True
b)False
Ans: a.

10) An array of arrays can be created.
a)True
b)False
Ans: a.

11) What is a string?
Ans: A combination of characters is called as string.

12) Strings are instances of the class String.
a)True
b)False
Ans: a.

13) When a string literal is used in the program, Java automatically creates instances of the string class.
a)True
b)False
Ans: a.

14) Which operator is to create and concatenate string?
Ans: Addition operator(+).

15) Which of the following declare an array of string objects?
String[ ] s;
String [ ]s:
String[ s]:
String s[ ]:
Ans : a, b and d

16) What is the value of a[3] as the result of the following array declaration?
1
2
3
4
Ans : d

17) Which of the following are primitive types?
byte
String
integer
Float
Ans : a.

18) What is the range of the char type?
0 to 216
0 to 215
0 to 216-1
0 to 215-1
Ans. D

19) What are primitive data types?
Ans : byte, short, int, long
float, double
boolean
char

20) What are default values of different primitive types?
Ans : int - 0
short - 0
byte - 0
long - 0 l
float - 0.0 f
double - 0.0 d
boolean - false
char – null

21) Converting of primitive types to objects can be explicitly.
a)True
b)False
Ans: b.

22) How do we change the values of the elements of the array?
Ans : The array subscript expression can be used to change the values of the elements of the array.

23) What is final varaible?
Ans : If a variable is declared as final variable, then you can not change its value. It becomes constant.
24) What is static variable?
Ans : Static variables are shared by all instances of a class.


FOR PLACEMENT

java questions

1.The Java interpreter is used for the execution of the source code.
True
False
Ans: a.

2) On successful compilation a file with the class extension is created.
a) True
b) False
Ans: a.

3) The Java source code can be created in a Notepad editor.
a) True
b) False
Ans: a.

4) The Java Program is enclosed in a class definition.
a) True
b) False
Ans: a.

5) What declarations are required for every Java application?
Ans: A class and the main( ) method declarations.

6) What are the two parts in executing a Java program and their purposes?
Ans: Two parts in executing a Java program are:
Java Compiler and Java Interpreter.
The Java Compiler is used for compilation and the Java Interpreter is used for execution of the application.

7) What are the three OOPs principles and define them?
Ans : Encapsulation, Inheritance and Polymorphism are the three OOPs
Principles.
Encapsulation:
Is the Mechanism that binds together code and the data it manipulates, and keeps both safe from outside interference and misuse.
Inheritance:
Is the process by which one object acquires the properties of another object.
Polymorphism:
Is a feature that allows one interface to be used for a general class of actions.

8) What is a compilation unit?
Ans : Java source code file.

9) What output is displayed as the result of executing the following statement?
System.out.println("// Looks like a comment.");
// Looks like a comment
The statement results in a compilation error
Looks like a comment
No output is displayed
Ans : a.

10) In order for a source code file, containing the public class Test, to successfully compile, which of the following must be true?
It must have a package statement
It must be named Test.java
It must import java.lang
It must declare a public class named Test
Ans : b

11) What are identifiers and what is naming convention?
Ans : Identifiers are used for class names, method names and variable names. An identifier may be any descriptive sequence of upper case & lower case letters,numbers or underscore or dollar sign and must not begin with numbers.

12) What is the return type of program’s main( ) method?
Ans : void

13) What is the argument type of program’s main( ) method?
Ans : string array.

14) Which characters are as first characters of an identifier?
Ans : A – Z, a – z, _ ,$

15) What are different comments?
Ans : 1) // -- single line comment
2) /* --
*/ multiple line comment
3) /** --
*/ documentation

16) What is the difference between constructor method and method?
Ans : Constructor will be automatically invoked when an object is created. Whereas method has to be call explicitly.

17) What is the use of bin and lib in JDK?
Ans : Bin contains all tools such as javac, applet viewer, awt tool etc., whereas Lib
contains all packages and variables.