Introduction to Java & BlueJ Environment
Q. The two types of Java programs/applications are? [2007] Ans: The two types of Java Applications are 'Internet Applets' and 'Stand alone application'.
Q. State the distinguishing features of Java and C++? Ans: (i) Java does not support operator overloading. (ii) Java does not use pointers. (iii) There are no header files in Java. (iv) Java does not have template classes as in C++.
Q. State the differences between Syntax errors and Logical errors. Ans: The compiler can only translate a program if the program is syntactically correct; otherwise the compilation fails and you will not be able to run your program. Syntax refers to the structure of your program and the rules about that structure. The second type of error is a run-time error, so-called because the error does not appear until you run the program. In Java, run-time errors occur when the interpreter is running the byte code and something goes wrong.
Q. "Object is an instance of a class", explain [2010] Ans: Object of a class contains data and functions provided in a class. it possesses all the features of a class. Hence object is termed as instance of a class.
Q. Name four basic features of JAVA. Ans: Basic features of Java as follows:i) It is an object oriented language.ii) Java program is both compiled and interpreted..iii) Java program can be application or applet.iv) java is case sensitive language, i.e. it distinguished upper and lower case letters.
Q. Differentiate between Compiler and Interpreter. Ans: Compiler convert source code to machine language whole at a time. Interpreter converts program from high level language to machine level language line by line or statement by statement.
Q. Java uses compiler as well as interpreter, explain. Ans: Java compiler converts Java source code to byte code. This byte code is further converted into machine code to make it applicable for the specific platform by using interpreter.
Q. Differentiate between Source code and Byte code. Ans: Source code is the program developed in Java Language, which is input to a computer through the keyboard. Compiler converts source code to byte code for interpretation.
Q. Differentiate between Testing and Debugging. Ans: Testing is the process of checking program logic manually to ensure whether it contains any error or not. Debugging is the process of removing errors from a program.
Q. Why is Java often termed as a platform?
Ans: Platform is the environment in which programs execute.
Instead of interacting with the Operating System directly, Java
programs runs on a virtual machine provided by Java, therefore
Java is often referred to as a platform also.
Q. What is a bytecode?
Ans: Bytecode is a set of pseudo mechanic language instructions
that are understood by the JVM (Java Virtual Machine) and are
independent of the underlying hardware.
Q. What do you understand by JVM?
Ans: JVM or Java Virtual Machine is an abstract machine designed
to be implemented on top of existing processors. It hides the
underlying OS from Java application. Programs written in Java
are compiled into Java byte-code, which is then interpreted by a
special java Interpreter for a specific platform. Actually this
Java interpreter is known as Java Virtual Machine (JVM).
Q. What is JDK (Java Development Kit)?
Ans: The Java development kit comes with a collection of tools
that are used for developing and running java programs.
Q. What are Java APIs?
Ans: The Java APIs (Application Program Interface) consist of
libraries of pre-compiled code that programmers can use in their
application.
Q. Write the five characteristics of Java/BlueJ?
Ans: 1. Write Once Run Anywhere 2. Light weight code 3. Security
4. Built in Graphics 5. Object Oriented Language 6. Support
Multimedia 7. Platform Independent. 8. Open Product.
Q. What do you know about BlueJ?
Ans: BlueJ is a Java development environment. It is an IDE
(Integrated Development Environment), which includes an editor a
debugger and a viewer.
Q. How you create, compile and execute a program in Java or
BlueJ? Explain your answer?
Ans: Create: Click on new class button from BlueJ editor, then
type the class name a program icon will be created. double click
on it, a program editor will be open, erase the code and type
your program coding. Compile: click the compile button on the
left of the window or right click on the class icon and select
compile from the menu options. Execute: Right click on the class
icon and select new class name option. A dialogue box appears
type the name of the object. A object icon will be created at
the bottom. Right click on the object icon and select the method
we want to execute.
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Conditionals and non-nested loops
Q. What is a statement?
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Q. What is an Object? Ans: An Object is an identifiable entity with some characteristics and behavior. E.g. take a class 'Car'. A car class has characteristics like colour, gears, power, length etc. now we create the object of that class 'Car' namely 'Indica'.
Q.
What is OOP? What are the features/concepts in OOP's?
OR Ans: The Object Oriented Programming Paradigm is the latest in the software development and the most adopted one in the programming development. The Paradigm means organising principle of a program. It is an approach to programming. The concepts of OOP's are: (1) Data Abstraction (2) Data Encapsulation (3) Modularity (4) Inheritance (5) Polymorphism.
Q. Explain all the Concepts of OOP's? Ans: Abstraction: It refers to the act of representing essential features without including the background details or explanation. Encapsulation: It is the way of combining both data and the function that operates on the data under a single unit. Modularity: It is the property of a system that has been decomposed into a set of cohesive and loosely couple modules. Inheritance: It is the capability of one class of thing to inherit properties from another class. Polymorphism: It is the ability for a message or data to be processed in more than one form.
Q. What are the advantages of OOP's? Ans: (1) Elimination of redundant coding system and usage of existing classes through inheritance. (2) Program can be developed by sharing existing modules. (3) Possibilities of multiple instance of an objects without any interference. (4) Security of data values from other segment of the program through data hiding.
Q. What is Class? How Object is related to the Class? Ans: A Class represent a set of Objects that share common characteristics and behavior. Objects are instance of a class. The Object represents the abstraction representation by the class in the real sense.
Q. What is the need of a class in Java? Ans: Classes in Java are needed to represent real-world entities, which have data type properties. Classes provide convenient methods for packing together a group of logical related data items and functions that work on them. In java the data items are called fields & the functions are called methods.
Q. What are Methods? How are these related to an Objects? Ans: A Method is an operation associated to an Object. The behavior of an Object is represented through associated function, which are called Methods.
Q. Point out the differences between Procedural Programming and Object Oriented Programming. Ans: Procedural programming aims more at procedures. The emphasis is a doing things rather then the data being used. In procedural Programming parading data are shared among all the functions participating thereby risking data safety and security. Object Oriented Programming is based on principles of data hiding, abstraction, inheritance and polymorphism. It implements programs using classes and objects, In OOP's data and procedure both given equal importance. Data and functions are encapsulated to ensure data safety and security.
Q. What is an abstraction? Ans: An abstraction is a named collection of attributes and behaviors required to represent an entity or concept for some particular problem domain.
Q. What is inheritance and how it is useful in Java. Ans: It is process by which objects of one class acquire the properties of objects of another class. Inheritance supports the concepts of hierarchical representation. In OOP the concepts of inheritance provides the idea of reusability.
Q. What role does polymorphism play as java feature? Ans: It mean the ability to take more than one form. For example, an operation, many types of data used in the operation.
Q. What is Data hiding? Ans: Data Hiding means restricting the accessibility of data associated with an object in such a way that it can be used only through the member methods of the object.
Q. What are nested classes? Ans: It is possible to define a class within another class, such classes are known as nested classes. A nested class has access to the members including private members of the class in which it is nested. However the enclosing class not have access to the members of the nested class.
Q. Differentiate between base and derived class. Ans: BASE CLASS - A class from which another class inherits (Also called SUPER CLASS) DERIVED CLASS - A class inheriting properties from another class. (Also called SUB CLASS)
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Class as the Basis of all Computation
Q. What are keywords? can keywords be used as a identifiers? Ans: Keywords are the words that convey a special meaning to the language compiler. No, keywords can never be used as identifiers.
Q. What is an identifier? What is the identifier formatting rule of Java? OR What are the rules for naming a variable? Ans: Identifiers are names given to different parts of a program e.g. variables, functions, classes etc. The identifiers in Java.(i) Can contains alphabets, digits, dollar sign and underscore.(ii) Must not start with a digit.(iii) Can not be a Java keywords.(iv) Can have any length and are case-sensitive.
Q. Why keyword is different from identifiers? Ans: Keywords are predefine sets of words that have a special meaning for the Java compiler. Identifiers on the other hand are created by Java programmers in order to give names to variables, function, classes etc.
Q. State the difference between Token and Identifier. Ans: The smallest individual unit of a program is known as Token. The following Tokens are available in Java: Keywords, Identifiers, Literals, Punctuations, Operators.Identifiers are names given to different parts of a program e.g. variables, functions, classes etc. The identifiers in Java.
Q. What are literals? How many types of integer literals are available in Java? Ans: A literal is sequence of characters used in a program to represent a constant value. For example 'A' is a literal that represents the value A of type char, and 17L is a literal that represents the number 17 as value of type long. Different types of literals available in Java, they are: Integer literal, Float literal, Boolean literal, Character literal, String literal and null literal.
Q. What is an integer constant? Write integer forming rule of Java. Ans: Integer constants are whole numbers without any decimal part. The rule for forming an integer constants is: An integer constant must have at least one digit and cannot contain a decimal point. It may contains + or - sign. A number with no sign is interpreted to be positive.
Q. What do you mean by Escape sequence and name few escape sequences in Java? Ans: Java have certain nongraphic characters (nongraphic characters are those characters that can not be typed directly from keyboard e.g. backspace, tab, carriage return etc.). Those nongraphic character can be represented by escape sequence. An escape sequence is represented by backslash followed by one or more character. The few escape sequence characters are: \n for new line, \t for Horizontal Tab, \v for Vertical Tab, \b for Backspace, \" for Double Quotes etc.
Q. How many integer constants are allowed in Java? How are they written? Ans: Java allows three types of integer constants: Octal (base 8), Decimal (base 10), and Hexadecimal (base 16). An Octal integer must be started with a zero '0', a Hexadecimal integer starts with a '0X', all others are treated as decimal integer constant.
Q. What is meant by a floating constant in Java? How many ways can a floating constant be represented into? Ans: Floating constants are real numbers. A floating constant can either be a fractional or in exponent form.
Q. Differentiate between Integer and Floating type constants. Ans: Integer constants are the whole numbers (without decimal points). e.g. 1231. Floating point constants are fractional numbers (number with decimal points). e.g. 14.2356
Q. What is a type or 'Data Type'? How this term is related to programming? Ans: A type or datatype represents a set of possible values. When we specify that a variable has certain type, we are saying what values the expression can have. For example to say that a variable is of type int says that integer values in a certain range can be stored in that variable.
Q. What is primitive data type? Name its different types. Ans: Primitive data types are those that are not composed of other data types. Numeric Integral, Fractional, character and boolean are different primitive data types.
Q. State the two kind of data types? [2006] Ans: The two types of data types are: Primitive and non-primitive/composite/user define data types. The primitive data types are: byte, short, int, long, float, double, char and Boolean. The non-primitive/reference data types are: class, array and interface.
Q. Write down the names of three primitive and three non-primitive/reference data types in Java/BlueJ. Ans: The primitive data types are: byte, short, int, long, float, double, char and Boolean. The non-primitive/reference data types are: class, array and interface.
Q. How many bytes occupied by the following data types: byte, short, int, long, float, double, char, boolean. Ans: char-2 byte, byte-1 byte, short-2 bytes, int-4 bytes, long-8 bytes, float-4 bytes, double-8 bytes, boolean-Java reserve 8 bits but only use 1 bit.
Q. What is the range of the following data types: byte, short, int, long, float, double, char, boolean. Ans: byte -> -128 to 127short -> -32768 to 32767int -> -231 to 231-1long ->-263 to 263-1float -> -3.4x1038 to 3.4x1038double -> -1.7x10308 to 1.7x10308char -> 0 to 65536boolean - > true or false
Q. What is the largest and smallest value for floating point primitive data types float? Ans: The smallest value is -3.4E+38 and largest values is 3.4E+38 of floating point data type.
Q. What is Token? What are the tokens available in Java? Ans: The smallest individual unit of a program is known as Token. The following Tokens are available in Java:- Keywords, Identifiers, Literals, Punctuations, Operators.
Q. What do you mean by variables? Ans: A variable is a named memory location, which holds a data value of a particular data types. E.g. double p;
Q. What do you mean by variables? What do you mean by dynamic initialization of a variable? Ans: A variable is a named memory location, which holds a data value of a particular data types. When a method or functions is called and the return value is initialise to a variable is called dynamic initialisation. example double p=Math.pow(2,3);
Q. What is the function of an operator? Ans: Operators are special symbols that represent operations that can be carried out on variables, constants or expressions.
Q. What do you mean by operator and write the name of all operators given in your textbook. Ans: The operations are represented by operators and the object of the operations are referred to as operands. The types of Operators available in Java are: 1. Arithmetic 2. Increment/Decrement 3. Relational 4. Logical 5. Shift 6. Bitwise 7. Assignment 8. Conditional 9. [] operator 10. new operator 11. (type) cast Operator 12. () operator. 13. dot operator.
Q. What are arithmetic operators? Ans: Arithmetical operators are used for various mathematical calculations. The result of an arithmetical expression is a numerical values. Arithmetical operators are of following types: Unary and Binary operators.
Q. Write major difference between the unary and binary operators? Ans: The operators that acts on one operand are referred to as Unary Operator. There are two Unary operators Unary + operator and Unary - operator. The operators that acts upon two operands are referred to as Binary Operator. The Binary Operators are Addition(+), Subtraction (-), Multiplication (*), Division (/) and Modulus (%).
Q. What is increment operator? What are postfix and prefix increment operators? Ans: The '++' operator is called increment operator. The increment operators add 1 to its operand. These are two types (i) Prefix and (ii) Postfix The prefix version comes before the operand for e.g. ++a, where as postfix comes after the operand e.g. a++
Q. Find the value of x after evaluating x += x++ + --x + 4 where x=3 before the evaluation. Explain your answer. Ans: Result is 13, because x++ is 3, --x is 2 + 4 the answer is 9 add this with x that is 3 it becomes 12 and due to pre increment of x++ the result becomes 13.
Q. What do you mean by Relational Operators. Ans: Relational operators are used to determine the relationship between different operands. These are used in work of compression also. The relational expression (condition) returns 0 if the relation is false and return 1 if the relation is true. < (less then), > (greater then), <= (less then equals to), >= (greater then equals to), == (equals to), != (not equals to).
Q. What is Logical operators? Ans: The logical operators combine the result of or more then two expressions. The mode of connecting relationship in these expressions refers as logical and the expressions are called logical expression. The logical expression returns 1 if the result is true otherwise 0 returns. The logical operators provided by Java are && Logical AND, || Logical OR, ! Logical NOT.
Q. What do you man by Assignment Statement or Assignment Operator? Ans: Assignment operator is represent by symbol '='. It takes the value on the right and stores it in the variable on the left side. for example x = y + 30
Q. What do you mean by Shift operators? OR Differentiate between Shift LEFT and Shift RIGHT operators. Ans: A Shift operators performs bit manipulation on data by shifting the bits of its first operand right to left. The shift operators available in Java are:(1) >> shift bits of right by distance. (signed shifting)(2) << shift bits of left by distance. (signed shifting)(3) >>> shift bits of right by distance (unsigned shifting)
Q. Differentiate between Shift LEFT and Shift RIGHT operators. Ans: Shift LEFT (<<) operatr shifts the bit pattern of the operand towards left by defined number of bits. Shift RIGHT (>>) operator shifts the bit pattern of the operand towards right by defined number of bits.e.g. 13>>2 is 3binary value of 13 is 1101>>2 is 0011 is equivalent to 3. Similarly LEFT shift (<<) operator is also work.
Q. What do you mean by Bitwise operators? Ans: The Bitwise operations are performed by Bitwise operator. The Bitwise operations calculate each bit of their result by comparing the corresponding bits of the two operands.(a) The AND operator &(b) The OR operator |(c) The XOR operator ^(d) The compliment operator ~
Q. Illustrate '?' operator with an example? Ans: It is a conditional operator, that stores a value depending upon a condition. This operator is also known as ternary operator. The syntax for this operator is expression1?expression2:expression3 . and the example is bonus=sales>15000?250:50;
Q. What is the purpose of new operator? Ans: We can use new operator to create a new objects or new array. Ex. myClass obj = new myClass();int arr[] = new int[5];
Q. What do you mean by precedence? Illustrate with the help of example. Ans: Precedence is the order in which a program evaluates the operations in a formula or expression. All operators have precedence value. An operator with higher precedence value is evaluated first then the operator having lower precedence value. consider the following example x = 5 + 4 *6;The value of this expression is 29 not 54 or 34. Multiplication has been performed first in this expression.
Q. What is operands? Ans: An operator acts on different data items/entities called operands.
Q. What do you mean by constant? How you declare a variable as constant variables. Ans: The memory variables/locations whose values can not be changed within the program is called constants. The keyword final makes a variable as constants.
Q. Which class is used for using different mathematical function in Java program? Ans: The class used for different mathematical functions in Java is java.lang.Math
Q. Write down the equivalent expression for the mathematical expression (a) (cos x/tan-1 x)+x (b) |ex - x| Ans: (Math.cos(x)/Math.atan(x)) + x and Math.abs(Math.exp(x)-x)
Q. What is the difference between these two function Math.ceil() and Math.rint(), explain with example. Ans: Math.ceil() this function returns the smallest whole number greater then or equal to the given number. e.g. Math.ceil(12.85) gives output 13 and Math.ceil(12.35) also gives output 13. Where as the Math.rint() returns the roundup nearest integer value. e.g. Math.rint(12.85) gives output 13 but Math.rint(12.35) gives output 12.
Q. What do you mean by type conversion? What is the difference between implicit and explicit type conversion explain with example. Ans: The process of converting one predefined type into another is called Type Conversion.A implicit type conversion is a conversion performed by the compiler. The Java compiler converts all operands up to the type of the largest operand. This is also known as type promotion. e.g. 'c'-32 is converted to int type. Where as an explicit type conversion is user defined that forces an expression to be of specific type, this also known as type casting. e.g. (float)(x+y/2)
Q. What is coercion? How it is implemented? Ans: Implicit type conversion of an expression is termed as coercion. A implicit type conversion is a conversion performed by the compiler. The Java compiler converts all operands up to the type of the largest operand. This is default type conversion.
Q. What do you mean by type casting? What is the type cast operator? Ans: The explicit conversion of an operand to a specific type is called type casting. The operator that converts its operand to a specified type is called the typecast operator. The typecast operator is ( ) in Java and is used as (type-to-be-converted-in)
Q. Explain the methods print() and println()? Ans: A computer program is written to manipulate a given set of data and to display or print the results. Java supports two output methods that can be used to send the results to the screen. print() method println() method.The print() method sends information into a buffer. This buffer is not flushed until a new line (or end-of-line) character is sent. As a result print() method prints output on one line.The println() method by contrast takes the information provided and displays it on a line followed by a line feed.
Q. What is an Expression? Explain its different types. Ans: An Expression is any statement which is composed of one or more operands and return a value. It may be combination of operators, variables and constants. There are three different types of expressions.(1) Constant Expressions: 8 * 12 /2(2) Integral Expressions: formed by connecting integer constants x = (a + b)/2(3) Logical Expressions: a > b or a!=b
Q. Mention two different styles of expressing a comment in a program. Ans: The two ways of inserting a comments in a program are: (i) using // single line comments (ii) using /* */ multiple line comments
Q. Differentiate between operator and expression. Ans: The operations are represented by operators and the object of the operations are referred to as operands. The expression is any valid combination of operators, constant and variables.
Q. What is a compound Statement? Give an Example. Ans: It is a block of code containing more then one executable statement. In Java the { } is called block and the statements written under {} is called compound statements or block statement. The { } opening and closing braces indicates the start and end of a compound statement. for(int i=1;i<=5;i++) { System.out.println("Hello"); System.out.println("How"); System.out.println("are you?"); }
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Q. What is constructor?
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Q. What is Function? Why do we use functions while programs
handling?
Q. What is the use of void before function name? [2007]
Q. Explain Functions/Methods Definitions with syntax?
Q. Why main() function so special?
Q. Explain the function prototype and the signature?
Q. Explain the function of a return statement? [2006]
Q. Write advantages of using functions in programs. [2010]
Q. Difference between Actual argument and Formal argument?
[2007,2008]
Q. What are static members?
Q. What is the use of static in main() methods? [2007]
Q. What is call by value? [2005]
Q. Explain the term "passed by reference"? [2007]
Q. Differentiate between call by value and call by reference?
Q. Define an impure functions? [2006]
Q. What is the difference between pure and impure functions? [2009]
Q. How are following passed in Java? [2005] (i)
primitive types (ii) reference types
Q. What does function overloading mean? What is its significance?
Q. Illustrate the concept of function overloading with the help of
an example. [2006]
Q. What is ‘this’ keyword? What is its significance? [2009]
Q. What do you mean by recursive function?
Q. What is the difference between Methods and Functions?
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Q. What is data type?
Q. What is composite (user define) data type?
Explain with an example? [2007] [2009]
Q. What is user define datatype?
Q. Can you refer to a class as a user defined
(composite) data type? [2009]
Q. What is the difference between primitive
data types and composite data types?
Q. Compare a class as a user defined data type
and class as an application?
Q. How are private member different from public
member of a class.
Q. How are protected members different from
public and private members of a class.
Q. Mention any two attributes required for
class declaration. [2008]
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Q. What are iteration statements? Name the
iteration statements provided by Java?
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