Note: Answer any five questions. Sun micro system officially describes java with a list of buzz words

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1 INTERNAL ASSESSMENT TEST I Date : Max Marks: 50 Subject & Code: JAVA & J2EE (10IS753) Section : A & B Name of faculty: M V Sreenath Time : AM 1.List and Explain features of Java. Note: Answer any five questions Sun micro system officially describes java with a list of buzz words or attributes. They are: - Simple & powerful - Safe - Object oriented - Robust - Architecture neutral - Compiled & Interpreted - Multithreaded - Easy to learn The salient features of Java are as follows: Simple & Powerful: To make the language familiar to the existing programming, java is modeled on C & C++. Java empowers you to express every idea you have in a clean objectoriented way.safe: Threat of viruses and abuse of resources are every where, java system not only verify the memory resources but also ensures that no viruses are communicated with the applet. Theabsence of pointers in java ensures that program can not gain access to memory location.object-oriented: Java is an object-oriented language. Almost every thing in java is object. All the program codes & data reside within object & classes.

2 Robust: Java is a strictly typed language, because the types must match exactly. It checks yourcode at compile time as well as at run time. Java is a garbage collected language, relieving theprogrammers all memory management problems ( i.e., deallocation is completely automatic). Java incorporates exception handling which captures series of errors and eliminates any riskof crashing the system. Architecture neutral: Java is the language that is not tied to any particular hardware or operating system. Program developed in java can be executed anywhere on any system. Youcan write once, run anywhere, anytime forever. Changes & upgrades in operating system, processors will not force any changes in java program. It works on Macintosh PC, UNIX &whatever the future platforms can offer. Interpreted: Java accomplishes architecture neutrality by compiling the java source code intoan intermediate code called byte codes, which can be interpreted on any system that has aproper java runtime on it.multithreaded: Java supports multithreaded programming which allows you to writeprograms that do many things simultaneously. Easy to learn: The language features feel like the natural way to do things & encourage goodprogramming style. Since object model is both mandatory & simple, you will quicklybecome acquainted with object oriented style of programming. BYTE Code is intermediate level code, which is interpreted by the JVM. It is

3 not directly

4 executable on the machine. This gives java it s write once and run anywhere nature. Whenjava program is written and compiled then it will create a.class file which consists of bytecode instructions, understandable to JVM. This class file is system independent. Every system has it s own JVM.so jvm will convert this byte code into machine language understandable to that system. So it has run write once and run anywhere nature. Java achieves architecture neutrality in the following way. Being platform independent wasone of the major objectives for java. Java achieves this independence by introducing anintermediate code representation of compiled java programs. Programs are compiled into abyte code which is then interpreted by platform specific interpreter. The byte code is same forany architecture, IBM compatible, Apple, Sparc, Sun Solaris. 2) a) Explain: i)>>> ii)short circuit logical operators iii)for each 1: : ================================================ : / / Overflow >>> 1 ================================================ : / / Unsigned shift right. Java provides two boolean operators boolean AND and boolean OR which are not provided by the other language and these operators are known as Short-Circuit logical operators. These operators gets the result of an logical operator, evaluating the right hand operator only if required. As per the Boolean Logical Table for a logical AND (&) operation, if the left hand (first) operand is false, then the result is false irrespective of the

5 right hand (second) operand. When short-circuit AND (&&) is used, if the first value is false, second value is not evaluated. Similarly for short-circuit OR ( ), if the first value is true, then second value is not evaluated. These short-circuit operators will be useful when we want to control the evaluation of right hand operand. if( denom!=0 && num / denom > 10 ) Here, the right hand expression num / denom > 10 will be evaluated only when denom is not zero, thus preventing divide by zero ArithmeticException. For-each is another array traversing technique like for loop, while loop, do-while loop introduced in Java5. It starts with the keyword for like a normal for-loop. Instead of declaring and initializing a loop counter variable, you declare a variable that is the same type as the base type of the array, followed by a colon, which is then followed by the array name. In the loop body, you can use the loop variable you created rather than using an indexed array element. It s commonly used to iterate over an array or a Collections class (eg, ArrayList) Syntax: for (type var : array) statements using var; Describe the process of building and running java program. Compiling Java Source Code Before the Java virtual machine (VM) can run a Java program, the program's Java source code must be compiled into byte-code using the javac compiler. Java byte-code is a platform independent version of machine code; the target machine is the Java VM rather than the underlying architecture. To compile a Java source code file Foo.java, you would do the following: % javac -g Foo.java

6 The -g command line option is optional, but we recommend using it as it makes debugging easier. If there are no errors in your source file, the Java compiler will produce one or more.class files (one.class file for each class defined in the Foo.java source file). For example, the results of a successful compile of Foo.java will produce a byte-code version of the class in a file named Foo.class. Every public class that you write must be in a separate.java file where the first part of the file name is identical to the class name. The.java file additionally can contain code for protected and private classes. We suggest that you get in the habit of using makefiles for compiling your Java application code. More information on makefiles is available here. Running a Java application Once you have successfully compiled your Java source code, you can invoke the Java VM to run your application's byte-code: % java <class with main method to run> [<comman d line args>,...] For example, to run the main method from the Foo class: % java Foo Any command line arguments (arguments to Foo's main method) follow the class name: % java Foo ) a) Describe the significance of final and super with examples. Usage of super class Super variables refer to the variable of variable of parent class. Super() invokes the constructor of immediate parent class. Super refers to the method of parent class. class employee int wt = 8; class clerk extends employee int wt = 10; //work time void display()

7 System.out.println(super.wt); //will print work t ime of clerk public static void main(string args[]) clerk c = new clerk(); c.display(); Final is a keyword in Java that is used to restrict the user and can be used in many respects. Final can be used with: Class Methods Variables final class stud // Methods cannot be extended to its sub class class books extends stud void show() System.out.println("Book-Class method"); public static void main(string args[]) books B1 = new books(); B1.show(); class stud final void show() System.out.println("Class - stud : method defined "); class books extends stud void show() System.out.println("Class - books : method define d"); public static void main(string args[]) books B2 = new books(); B2.show();

8 import java.util.*; import java.lang.*; import java.io.*; class stud final int val; stud() val = 60; void method() System.out.println(val); public static void main(string args[]) stud S1 = new stud(); S1.method(); 4)a) What is an inner class? Write a program to demonstrate inner class. b) Explain the java's built in exceptions. Java inner class or nested class is a class which is declared inside the class or interface. We use inner classes to logically group classes and interfaces in one place so that it can be more readable and maintainable. Additionally, it can access all the members of outer class including private data members and methods. Advantage of java inner classes There are basically three advantages of inner classes in java. They are as follows: 1) Nested classes represent a special type of relationship that is it can access all the members (data members and methods) of outer class including private. 2) Nested classes are used to develop more readable and maintainable code because it logically group classes and interfaces in one place only. 3) Code Optimization: It requires less code to write. Built-in exceptions are the exceptions which are available in Java libraries. These exceptions are suitable to explain certain error situations. Below is the list of important built-in exceptions in Java.

9 Arithmetic Exception It is thrown when an exceptional condition has occurred in an arithmetic operation. ArrayIndexOutOfBoundException It is thrown to indicate that an array has been accessed with an illegal index. The index is either negative or greater than or equal to the size of the array. ClassNotFoundException This Exception is raised when we try to access a class whose definition is not found FileNotFoundException This Exception is raised when a file is not accessible or does not open. IOException It is thrown when an input-output operation failed or interrupted InterruptedException It is thrown when a thread is waiting, sleeping, or doing some processing, and it is interrupted. NoSuchFieldException It is thrown when a class does not contain the field (or variable) specified NoSuchMethodException It is thrown when accessing a method which is not found. NullPointerException This exception is raised when referring to the members of a null object. Null represents nothing 5)What is a package? What are the steps involved in creating user defined packages? package is a keyword of Java followed by the package name. Just writing the package statement followed by the name creates a new package; see how simple Java is to practice. For this reason, Java is known as a production language. While create User Defined Packages Java, the order of statements is very important. The order must be like this, else, compilation error. 1. Package statement 2. Import statement 3. Class declaration

10 If exists, the package statement must be first one in the program. If exists, the import statement must be the second one. Our class declaration is the third. Any order changes, it is a compilation error. When the code is ready, the next job is compilation. We must compile with package notation. Package notation uses d compiler option as follows. C:\snr > javac -d. Tiger.java The d compiler option creates a new folder called forest and places the Tiger.class in it. The dot (.) is an operating system's environment variable that indicates the current directory. It is an instruction to the OS to create a directory called forest and place the Tiger.class in it. 6)a) How are arrays defined and used in java. b) Discuss labeled break and continue statements. Syntax arrayrefvar = new datatype[arraysize]; The above statement does two things It creates an array using new datatype[arraysize]. It assigns the reference of the newly created array to the variable arrayrefvar. Declaring an array variable, creating an array, and assigning the reference of the array to the variable can be combined in one statement, as shown below datatype[] arrayrefvar = new datatype[arraysize]; Alternatively you can create arrays as follows datatype[] arrayrefvar = value0, value1,..., valu ek; The array elements are accessed through the index. Array indices are 0-based; that is, they start from 0 to arrayrefvar.length-1. Example Following statement declares an array variable, mylist, creates an array of 10 elements of double type and assigns its reference to mylist double[] mylist = new double[10];

11 Using break statement : When a break statement is encountered inside a loop, the loop is terminated and program control resumes at the next statement following the loop. Here is a simple example: /** * This program demonstrates * break to exit a loop. */ public class BreakDemo public static void main(string[] args) for (int i = 1; i <= 10; i++) if (i == 5) break; // terminate loop if i is 5 System.out.print(i + " "); System.out.println("Loop is over."); b) What is meant by instance variable hiding? How to overcome it? 7)What is an exception? Explain the different exception handling mechanisms with an example This is the general form of an exception-handling block: try //block of code to be monitored for errors catch (ExceptionType1 exob ) //exception handler for ExceptionType1

12 catch (ExceptionType2 exob ) //exception handler for ExceptionType2

13 //... finally //block of code to be executed before try block ends DIVIDE-BY-ZERO EXCEPTION This small program has an expression that causes a divideby-zero error. class DivideByZero public static void main (String args[]) int d = 0; int a = 42 / d; The Java run-time system constructs a new exception object when it detects an attempt to divide-by-zero. It then throws this exception. In the above example, there is no exceptional handler to catch the exception. The default handler provided by the Java run-time system will process any exception that is not caught by a program. The output of the above program when

14 executed by the standard Java JDK runtime interpreter: java.lang.arithemeticexception:/ by zero at DivideByZero.main(DivideByZero.java:4) Although the default exception handler is provided by Java run-time system, you will usually like to handle exception yourself. The following program includes a try block and a catch clause, which processes the ArithmeticException generated by the divisionby-zero: class DivideByZero public static void main (String args[]) int d, a; try //monitor a block of code d = 0; a = 42 / d; System.out.println("This will not be printed. "); catch(arithmeticexception e) System.out.println("Division by zero.");

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16 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Information Science and Engineering System.out.println("After catch statement."); This program generates the following output: Division by zero. After catch statement The call to println() inside the try block is never executed.once an exception is thrown, program control transfers out of the try block into the catch block. Once the catch statement has executed, the program continues with the next line in the program following the entire try/ catch mechanism. 8) a) Differentiate between the usage of access specifiers in java and their scope. b) With an example explain overloading and overriding. Java provides 3 types of access specifiers. public: public keyword applied to a class, makes it available/visible everywhere. Applied to a method or variable, completely B.E VII semester

17 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Information Science and Engineering visible. Example: public int number; public void sum( ). private: private fields or methods for a class only visible within that class. Private members are not visible within subclasses, and are not inherited. protected: protected members of a class are visible within the class, subclasses and also within all classes that are in the same package as that class and also to subclasses in other packages. friendly(default): when no access modifier is specified, the members defaults to friendly level of access. It makes fields visible within the class, subclasses and also within all classes that are in the same package as that class. b) With an example explain overloading and overriding. Overloading vs Overriding in Java 1. Overloading happens at compile-time while Overriding happens at runtime: The binding of overloaded method call to its definition has happens at B.E VII semester

18 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Information Science and Engineering compile-time however binding of overridden method call to its definition happens at runtime. 2. Static methods can be overloaded which means a class can have more than one static method of same name. Static methods cannot be overridden, even if you declare a same static method in child class it has nothing to do with the same method of parent class. 3. The most basic difference is that overloading is being done in the same class while for overriding base and child classes are required. Overriding is all about giving a specific implementation to the inherited method of parent class. 4. Static binding is being used for overloaded methods and dynamic binding is being used for overridden/overriding methods. 5. Performance: Overloading gives better performance compared to overriding. The reason is that the binding of overridden methods is being done at runtime. 6. private and final methods can be overloaded but they cannot be overridden. It means a class can have more than one private/final methods of same name but a child class cannot override the private/final methods of their base class. 7. Return type of method does not matter in case of method overloading, it can be same or different. However in case of method overriding the overriding method can have more specific return type 8. Argument list should be different while doing method overloading. Argument list should be same in method Overriding. B.E VII semester