Vidyalankar. T.Y. Diploma : Sem. V [CO/CM/IF] Java Programming Time : 3 Hrs.] Prelim Question Paper Solution [Marks : 100

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1 T.Y. Diploma : Sem. V [CO/CM/IF] Java Programming Time : 3 Hrs.] Prelim Question Paper Solution [Marks : (a) (i) FEATURES OF JAVA 1) Compiled and interpreted 2) Platform independent and portable 3) Object Oriented 4) Robust and secure 1) Compiled and interpreted : Usually a computer language is either compiled or interpreted. Java combines both these approaches thus making Java a two-stage system. First, java compiler translates source code into what is known as bytecode instructions. Bytecodes are not machine instructions and therefore, in the second stage, Java interpreter generates machine code that can be directly executed by the machine that is running the Java program. We can thus say that Java is both a compiled and an interpreted language. [1 Mark] 2) Platform independent and portable : The most significant contribution of java over other languages is its portability. Java programs can be easily moved from one computer system to another, anywhere and anytime. Changes and upgrades in operating systems, processors and system resources will not force any changes in java programs. This is the reason why java has become a popular language for programming on Internet which interconnects different kinds of system worldwide. [1 Mark] Java ensures portability in two ways. First, Java compiler generates bytecode instructions that can be implemented on any machine. Secondly the size of the primitive data types are machine independent. 3) Object oriented : Java is a true object oriented language. Almost everything in Java is an object. All program code and data reside within objects and classes. Java comes with an extensive set of classes, arranged in packages that we can use in our programs by inheritance. The object model in Java is simple and easy to extend. [1 Mark] 4) Robust and Secure : Java is robust language. It provides many safeguards to ensure reliable code. It has strict compile time and run time checking for data types. It is designed as a garbage collected language relieving the programmers virtually all memory management problems. Java also incorporates the concept of exception handling which captures series errors and eliminates any risk of crashing the system. [1 Mark] Security becomes an important issue for a language that is used for programming on internet. Threat of viruses and abuse of resources is everywhere. Java system no only verify all memory access but also ensure that no viruses are communicated with an applet. The absence of pointers in java ensures that programs cannot gain access to memory locations without proper authorization. (ii) SYNCHRONIZATION Consider a situation when threads may compete for the same resources. For example, one thread may try to read a record from a file while another is still writing to the same file. Depending on the situation, we may get strange results. Java enables us to overcome this problem using a technique known as synchronization. 1. (a) In java, the keyword synchronized helps to solve problems of concurrency. e.g. the method that will read information from a file and the method that will update the same file maybe declared as synchronized. 1

2 : T.Y. Diploma JP Example: Synchronized void update ( ) // code here is synchronized 1. (a) 1. (a) When we declare a method synchronized, Java creates a monitor and hands it over to the thread that calls the method 1st time. As long as the thread holds the monitor, no other thread can enter the synchronized section of code. Whenever, a thread has completed its work of using synchronized method (or block of code), it will hand over the monitor to the next thread that is ready to use the same resource. (iii) PACKAGE We must first declare the name of the package using the package keyword followed by the package name. This must be first statement in a Java source file. Then we define a class, just as we normally define a class. Example : package first Package public class FirstClass (body of class) Here the package name is first package. The class first class is now considered a part of this package. This listing would be saved as a file called Firstclass. Java and located in a directory named firstpackage. When the source file is completed. Java will create a class file and store it in the same directory. Creating our own package involves the following steps i) Declare the package at the beginning of a while using the form. Package packagename ii) Define the class that is to be put in the package and declare it public. iii) Create a subdirectory under the directory where the main source files are stored. iv) Store the listing as the classname java file in the subdirectory created. v) Compile the file. This creates class file in the subdirectory. Java also supports the concept of package hierarchy. This is done by specifying multiple names in a package statement, separated by dots. Example : package FirstPackage. SecondPackage ; This approach allows us to group related classes into a package and then group related packages into a larger package. Remebember to store this package in a subdirectory named First package / Secondpackage. (iv) APPLETS are small Java programs that are primarily used in Internet computing. They can be transported over the Internet from one computer to another and run using the Applet viewer or any web browser that supports Java. [1 Mark] Local and Remote Applets: An applet developed locally and stored in a local system is known as a local applet. When a web page is trying to find a local applet, it does not need to use the Internet. A remote applet, it does not need to use the Internet. A remote applet is that which is developed by someone else and stored on a remote computer connected to the Internet. We can download the remote applet onto our system via the Internet and run it. In order to locate and load a remote applet, we must know the applets address on the web. This address is known as Uniform Resource Locator (URL). [3 Marks] 2

3 Prelim Question Paper Solution 1. (b) 1. (b) (i) Class Fibonacci public static void main (String args [ ] ) int n, f 1, f 2, f 3 ; int a ; f 1 = f 2 = 1 ; System. out. println (f f 2 ) ; n = 3 ; while (n < = 10) f 3 = f 1 + f 2 ; System. out. println (f 3 + ) ; f 1 = f 2 ; f 2 = f 3 ; + + n ; [4 Marks] (ii) COMMAND LINE ARGUMENTS [3 Marks] The parameters or arguments given to a program when invoked for execution at the command line is defined as command line argument. Consider Public static void main (string args [ ]) Args declared as an array of strings. Any arguments provided in the command line at the time of execution are passed to the array args. Java Test BASIC FORTRAN C + + Java. This command line contains four arguments. These are assigned to the array args as follows: BASIC args [0] FORTRAN args [1] C + + args [2] JAVA args [3] The individual elements of an array are accessed by using an index or subscript like args [i]. For example, args [2] represents C + + The program uses command line arguments as input is as follows: Class comline Test public static void main (string args (1) int count, i = 0; String string; count = args. length; System.out.println ( number of arguments = +count while (i (count) string = args [i]; i = i + 1; system.out.println (i + : + Java is + string+! ); [3 Marks] 3

4 : T.Y. Diploma JP Compile and run the program with the command line as follows: Java comline Test simple object oriented Distributed Robust secure portable multithreaded Dynamic. 2. (a) The output of the program would be as follows: Number of arguments = 8 Java is simple Java is object oriented! Java is Distributed! Java is Robust! Java is secure! Java is portable! Java is multithreaded! Java is Dynamic! TRY, THROW AND CATCH The code which is expected to generate the exception must be enclosed in the try and catch block. The very basic form of the exception-handling block is the following : try //statements //statements catch(<exceptiontypeclass> object1) //statements to handle the exception Inside the try and catch block, as soon as the exception condition arises, an object of that specific type of exception is automatically created and thrown. The thrown object is then matched with the appropriate catch block, i.e. the catch block having the same parameter type as the object thrown. If the block matches, then the statements for handling the exception written within the catch block are executed. Consider the following program, which demonstrates how the runtime environment handles an exception when it is generated? It is further modified to handle the exception through the code itself. The exception raised is the NumberFormatException. It arises when you try to convert a string to number format, and the string is either empty or does not contain the number in a proper format. class NumFormExcp public static void main(string args[ ]) String str1 = new String("text12"); int num1 = Integer.parseInt(str1); //converts string to number System.out.println(num1); The output is: Exception in thread "main" java.lang.numberformatexception: text12 at java.lang.integer.parseint(compiled Code) at java.lang.integer.parseint(integer.java:458) at numformexcp.main(numformexcp.java:6) 4

5 Prelim Question Paper Solution THROWS Till now we have seen that an exception is thrown either implicitly or explicitly in the try block and there is a catch block ready to handle it. But there are methods, which throw the exception, but do not catch it within the method body. In this case the method which is throwing the exception must use a throws clause with its definition. The throws clause acts as warning message which makes the calling module aware that the called module is throwing an exception which it is not handling, and it has to handle the thrown exception. In case of runtime exceptions, the method that leaves them unhandled need not use throws clause, the runtime environment will handle them. Consider the following class structure that has a method, namely, method_one(). This method is using the throws clause which is throwing an exception object. Note that in the same method there is no subsequent catch clause. This method is being called from the main() method which in turn is made to catch the exception thrown by method_one(), though main() is not responsible for throwing it directly. Now if the main() method is not handling this exception it can now specify a throws clause and let the exception be handled by the runtime environment. class <classname> static void method_one() throws <exception_one> throw new <exception_one> // method1 is throwing the exception, // but not catching it public static void main(string args[ ]) try method_one(); // main() is not throwing the //exception, but it has to catch //it catch(<exception_one> object) //Statements for exception handling FINALLY The finally clause is written with the try statement, rather the try statement must have either the catch or the finally block, and having both of them within the try statement is also not a bar. The benefit of the finally block is that it is definitely executed after a catch block or before the method quits. This takes the form as : try //statements finally //statements or try //statements catch(<exception> obj) 5

6 : T.Y. Diploma JP 6 //statements finally //statements Take a look at the following example which has a catch and a finally block. The catch block catches the ArithmeticException which occurs for arithmetic error like divide-byzero. After executing the catch block the finally is also executed and you get the output for both the blocks. class Finally_Block static void division() try int num = 34, den = 0; int quot = num / den; catch(arithmeticexception e) System.out.println("Divide by zero"); finally System.out.println("In the finally block"); public static void main(string args[ ]) division( ); The output of the above program is : Divide by zero In the finally block. 2. (b) DYNAMIC DISPATCH METHOD Method overriding forms the basis for one of java s most powerful concept dynamic method dispatch. Dynamic method dispatch is the mechanism by which a call to a overridden method is resolved at run time rather than at compile time. This shows how java implements run time polymorphism. As you know a superclass reference variable can refer to a subclass object. Java uses this fact to resolve calls to overridden method at run time. When a overridden method is called through a superclass reference java determines which method to execute based upon the type of the object being referred at the time the call is made. [3 Marks] Program Class A Void Show ( ) System. out. println ( in show of A ) ;

7 Prelim Question Paper Solution 2. (c) Class B extends A Void Show ( ) System. out. println ( in show of B ) ; Class C extends B void show ( ) System. out. println ( in show of C ) ; Class DynaMethod public static void main (String args [ ]) A a = new A ( ) ; B b = new B ( ) ; C c = new C ( ) ; A r ; r = a ; r. show ( ) r = b ; r. show ( ) r = c ; r. show ( ) ; [5 Marks] STREAMS Java programs perform I/O through streams. A stream is an abstraction that either produces or consumes information. A stream is linked to a physical device by the Java I/O system. All streams behave in the same manner, even if the actual physical devices to which they are linked differ. Thus, the same I/O classes and methods can be applied to any type of device. This means that an input stream can abstract many different kinds of input: from a disk file, a keyboard, or a network socket. Likewise, an output stream may refer to the console, a disk file, or a network connection. Streams are a clean way to deal with input/output without having every part of your code understand the difference between a keyboard and a network, for example. Java implements streams within class hierarchies defined in the java.io package. Byte Streams and Character Streams Java 2 defines two types of streams: byte and character. Byte streams provide a convenient means for handling input and output of bytes. Byte streams are used, for example, when reading or writing binary data. Character streams provide a convenient means for handling input and output of characters. They use Unicode and, therefore, can be internationalized. Also, in some cases, character streams are more efficient than byte streams. The original version of Java (Java 1.0) did not include character streams and, thus, all I/O was byte-oriented. Character streams were added by Java 1.1, and certain byte-oriented classes and methods were deprecated. This is why older code that doesn't use character streams should be updated to take advantage of them, where appropriate. One other point: at the lowest level, all I/O is still byte-oriented. The character-based streams simply provide a convenient and efficient means for handling characters. An overview of both byte-oriented streams and character-oriented streams is presented in the following sections. [3 Marks] The Character Stream Classes Character streams are defined by using two class hierarchies. At the top are two abstract classes, Reader and Writer. These abstract classes handle Unicode character streams. Java has several concrete subclasses of each of these. The abstract classes Reader and Writer define several key methods that the other stream classes implement. Two of the most important methods are read( ) and write( ), which read and write characters of data, respectively. These methods are overridden by derived stream classes. [3 Marks] 7

8 : T.Y. Diploma JP 2. (d) 3. (a) 8 Class Even extends Thread public void run ( ) try for (int i = 2 ; i < 20 ; i = i + 2) System. out. println ( \t Even thread : + i) Thread sleep (500), Catch (InterruptedException e) Class Odd extends Thread public void run ( ) try for (int i = 1 ; i < 20 ; i = i + 2) System. out. println ( It odd Threds: +i) Thread. sleep (500) ; Catch (InterruptedException e) Class Evenodd public static void main (String args [ ]) new Even( ). Start ( ) ; new Odd ( ). Start ( ) ; System. out. println ( Exit from main ) ; [8 Marks] Functionality of a FILE class i) In java file is represented by a class. ii) This class abstracts the properties like size, permissions, time and date of creation and last modification and also information regarding directory path. The class file has methods to retrieve this information about a file. iii) The files are stored and retrieved by the file system. We have seen that the list of files displayed by dir command. iv) They will list all the files in the directories with their attributes of a file. Note that the class file cannot change the way information is stored in a file or the way in which information is retrieved from a file. The class file interacts with files and file systems to get the attributes of a file. v) A directory denotes a group of files or directories. The class file can represent both files and directories. vi) The class file has the following constructors: File (String dirpath) : Creates an instance of class File with the Specified directory path. Example File f1 = new File ( C : \\ Riddhi )

9 vii) The above statement creates one object f1 of file with directory Riddhi. File (String dirpath, String filename) : In this form of constructor both directory path and file name are specified. Example File f1 = new file ( C \\ Riddhi, Tanmay. java) ; viii) The above statement creates one object f1 of File with file Tanmay. java : File (File dir, String filename) : Prelim Question Paper Solution This form is similar to the previous one but here directory is specified as another file object. Example File f1 = new file ( C : \\ Riddhi ) ; File f2 = new file (f1 Tanmay. java ) ; ix) Here f1 is the object of file class with Directory which is passed in f2 while creating the object of f2 and Tanmay. java is the name of the file in that directory. 3. (b) It is simple to add a class to an existing package. Consider the following package. package p1 ; public class A // body of A The package p1 contains one public class by name A. Suppose we want to add another Class B to the package. This can be done as follows: i) Define the class and make it public. ii) Place the package statement. package p1 public Class B // body of B iii) Store this as B. Java file under the directory p1. iv) Compile B. java file. This will create a B. class file and place it in the directory p1. Note that we can also add non public class to a package using the same procedure. Now, the package p1 will contain both classes A and B. A statement like, import p1. * ; will import both of them. Remember that, since a java source file can have only one class declared as public, we cannot put or more public classes together in a java file. This is because of the restriction that the file name should be same as the public class with java extensions. It we want to create a package with the multiple public classes in it, we may follow the following steps : i) Decide the name of the package. ii) Create the subdirectory with this name under the directory where main source file are stored. iii) Create classes that are to be placed in the package in separate source files and declare the package statement, package packagename ; at the top of each source file. iv) Switch to the subdirectory created earlier and compile each source file. When completed, the package would contain class files of all the source files. What are Thread? A thread is similar to a program that has a single flow of control. It has a beginning, a body, and an end, and executes commands sequentially. Java enables us to use multiple flows of control in 3. (c) 9

10 : T.Y. Diploma JP developing programs. Each flow of control may be thought of us as separate tiny program (or module) known as a thread that runs in parallel to others. The ability of a language to support multithreads is referred to as concurrency. Since threads in Java are subprograms of a main application program and share the same memory space, they are known as lightweight threads or lightweight processors. Under single processing environment, threads running in parallel, does not really mean that they actually run at the same time. Since all threads are running on a single processor, the flow of execution is shared between the threads. The java interpreter handles the switching of control between the threads in such a way that it appears they are running concurrently. Why use Thread? i) It enables programmers to do multiple things at one time. ii) They can divide a long program (containing operations that are conceptually concurrent) into threads and execute there in parallel. iii) Threads are extensively used in Java enabled browsers such as Hot Java. These browsers can download a file to the local computer, display a web page in the window, output another web page to a porter and so on. [The run ( ) method is the heart and soul of any thread. Creating and Running Thread A new thread can be created in two ways. i) By creating a thread class : Define a class that extends thread class and override its run ( ) method with the code required by the thread. ii) By converting a class to a thread : Define a class that implements Runnable interface. The Runnable interface has only one method, run ( ), that is to be defined in the method with the code to be executed by the thread. (A) Extending the Thread Class : We can make our class runnable as a thread by extending the class java long thread. This gives us access to all the thread methods directly. It includes the following steps. i) Declare the class as extending the thread class. class My Thread extends Thread // body of My Thread ii) Implement the run ( ) method that is responsible for executing the sequence of code that the thread will execute. The run ( ) method has been inherited by the class My Thread. We have to override this method in order to implement the code to be executed by our thread. Public void run ( ) // Thread code here iii) Create a thread object and call the start ( ) method to initiate the thread execution. My Thread a Thread = new My Thread ( ); a Thread.start ( ); // invokes run ( ) method The first line instantiates a new object of class My Thread. The thread object is not yet running. The thread is in a newborn state. The second line calls the start ( ) method causing the thread to more into the runnable state. Then, the Java runtime will schedule the thread to run by invoking its run ( ) method. Now, the thread is said to be in the running state. 10

11 3. (d) 3. (e) Prelim Question Paper Solution GARBAGE COLLECTION When the object is not needed any more, the space occupied by such objects can be collected and used for later reallocation. Java performs release of memory occupied by unused objects automatically, it is called garbage collection. JVM runs the garbage collector when it finds time. Garbage collector will be run periodically but you can not define when it should be called. We can not ever predict when this method will be executed. It will get executed when the garbage collector, which runs on its own, picks up the object. Program Class x int a ; x ( ) a = 0 ; Class y public static void main (String args [ ]) x ob1 = new x ( ) ; x ob2 = new x ( ) ; ob1 = ob2 ; See the above program here the two objects are created which are referenced by ob1 and ob2 as, Ob1 a = 0 Ob2 * Representation of Ob1 and Ob2 a = 0 After the execution of the statement, ob1 = ob2 ; a = 0 a = 0 * Representation of Ob1 and Ob2 to same object Java packages are classified as java API PACKAGES and user defined packages. Java API packages are: i) java.lang ii) java.util iii) java.io iv) java.awt v) java.net vi) java.applet Package first package; // package declaration Public class Firstclass // class definition (body of class) The step to create the package are as follows: i) Create Subdirectory or Directory with the package name. ii) Define as many classes as required with only on class defined as public. iii) Compile the file with the class name under the subdirectory. This create class file in the subdirectory. 11

12 : T.Y. Diploma JP 4. (a) (i) Inputstrean and reader classes Inputstream is an abstract class that defines Java s model of streaming byte input. All of the methods in this case will throw an IOException on error conditions. Method void close ( ) : Closes the input source. Further read attempts will generates an IOException. void mark(int numbytes) : Places a mark at the current point in the inputstream that will remain valid until num Bytesbytes are read. Reader is an abstract class that defines Java s model of streaming character input. All of the methods in this class will throw an IOException on error conditions. abstract void close( ) : Closes the input source. Further read attempts will generate an IOException. void mark(int numchars) : Places a mark at the current point in the input stream that will remain valid until numchars characters are read. Outputstream and Writer classes Outputstream is an abstract class that defines streaming byte output. All of the methods in this class return a void value and throw an IOException in the case of errors. Methods void close( ) : Closes the output stream. Further write attempts will generate an IOException. void flush( ) : Finalizes the output state so that any buffers are cleared. That is, it flushes the output buffers. 4. (a) (ii) Class Palindrome public static void main (String args[ ]) throws IOException BufferedReader br = new BufferedReader (new InputStreamReader system.in); System.out.println ( Enter the no. for checking ); try StringBuffer S = new StringBuffer(br.readLine( )); Catch ( ) System.out.println ( Improper Input ) ; String Buffer S1 = new StringBuffer (S) ; S1.reverse ( ); if (s.equals(s1)) System.out.println ( It is palindrome ); else System.out.println ( It is no palindrome ); [4 Marks] 4. (a) (iii) Newborn state : When we create a thread object, the thread is born and is said to be in newborn state. Runnable state : The runnable state meant that the thread is ready for execution and is waiting for the availability of the processor. 12

13 Prelim Question Paper Solution yield ( ) Running thread 4. (a) Runnable thread Running state : Running means that the processor has given its true to the thread for its execution. The thread runs until it relinquishes control on its own or it is free by a higher priority thread. Blocked state : A thread is said to be blocked when it is prevented from entering into the runnable state and subsequently the running state. This happens when the thread is suspended, sleeping, or waiting in order to satisfy certain requirements. A blocked thread is considered not runnable but not dead and therefore fully qualified to run again. Dead state : Every thread has a life cycle. A running thread ends its life when it has completed executing its run ( ) method. (iv) Java defines several built-in classes for exception handling. All these classes are a part of the java.lang package which is automatically imported. That is why, while throwing the exceptions you did not specifically include any package for exception classes. Apart from the built-in exception classes you can define your own exception classes. This is very useful when you want to define exception types which are having a behaviour different from the standard exception types, particularly when you want to do validations in your application. The example given below creates a user-defined exception and uses it. In this example the exception class is created and used in the same. java file, but it is possible to create and store exception types in packages and use them globally. class Validate_Range extends Exception String mesg; validate_range() mesg = new String("Enter between 20 and 100"); public String tostring() return (mesg); public class My_Exception public static void main(string args[ ]) try int x = 10; if( x < 20 x > 100) throw new Validate_Range(); catch(validate_range e) System.out.println(" ** " + e); 13

14 : T.Y. Diploma JP 4. (b) The exception class here is the Validate_Range class. You must have noticed that this class is derived from the Exception class. For any class to behave as an exception type it must become the subclass of the Exception class. A variable mesg of String type is defined and in the constructor it is initialized with appropriate message. You are also overriding the function tostring so that the caught exception object can convey some message when used in a print statement. Refer to the statement: System.out.println(" ** " + e); Now the class My_Exception is able to throw and catch the Validate_Range exception. (i) APPLET LIFE CYCLE Every Java applet inherits a set of default behaviours from the applet class. The applet state includes: (a) Born or Initialisation state (b) Running state (c) Idle state (d) Dead or destroyed state Begin (Load Applet) Display start ( ) Born Running Paint ( ) Initialization stop ( ) start ( ) Destroyed [3 Marks] (a) Initialization state: Applet enters the initialization state when it is first loaded, by calling the init ( ) method of Applet class. The initialization occurs only once in the applets life cycle. We must override the init ( ) method, to perform initialization of variables. public void init ( ) // action. (b) Running state: Applet enters the running state when the system calls the start ( ) method of applet class. This takes place automatically. Starting can also occur when the applets is in stopped or idle state. For Example, we may leave the webpage containing the applet temporarily to another page and return back to the page. This again starts the applet running. public void start ( ) Idle Dead Stopped destroy ( ) Exit of Browser End 14

15 Prelim Question Paper Solution // Action (c) Idle a stopped state: An applet becomes idle when it is stopped from running. Stopping occurs automatically when we leave the page containing the currently running applet or by calling the stop ( ) method explicitly. public void stop ( ) // body of Action (d) Dead state: An applet is said to be dead when it is removed from memory. This occurs automatically by invoking the destroy ( ) method when we quit the browser. If the applet has created any resources, like threads, we may override the destroy ( ) method to clear up these resources. public void destroy ( ) // body of Action [3 Marks] 4. (b) (ii) import java.util.*; Class VectorDemo Vector v = new vector (7); V.addElement (new Integer (1)); V.addElement (new Integer (2)); V.addElement (new String ( abc )); V.addElement (new String ( xyz )); V.addElement (new Float (5.4)); V.addElement (new Float (6.2)); V.addElement (new Float (7.3)); System.out.println ( Seven element added ); V.removeElementAt (3); System.out.println ( 3 rd position element is removed ) V.insertElement (new String ( abb ), 5); System.out.println ( New element is added in 5 th position ); Enumeration venum = v elements ( ); System.out.pritln ( /n Elements in vector ); while (venum.hasmore.elements ( )) System.out.println (Enum.nextElement ( ) + ); System.out.println ( ); Output Elements in vector 1 2 xyz 5.4 abb drawoval( ) void drawoval(int top, int left, int width, int height) filloval( ) void filloval(int top, int left, int width, int height) [6 Marks] 5. (a) 15

16 : T.Y. Diploma JP import java.awt.*; import java.applet.*; /* <applet code = Ellipses width = 300 height = 200> </applet> */ public class Ellipse extends Applet public void paint(graphics g) g.drawoval(10, 10, 50, 50); g.filloval(100, 10, 75, 50); g.drawoval(190, 10, 90, 30); g.filloval(70, 90, 140, 100); Drawrect( ) void drawrect(int top, int left, int width, int height) import java.awt.*; import java.applet.*; /* <applet code= Rectangles width = 300 height = 200> </applet> */ public class Rectangles extends Applet public void paint(graphics g) g.drawrect(10, 10, 60, 50); g.fillrect(100, 10, 60, 50); g.drawroundrect(190, 10, 60, 50, 15, 15); g.fillroundrect(70, 90, 140, 100, 30, 40); Drawline( ) void drawline(int startx, int starty, int endx, int endy) import java.awt.*; import java.applet.*; /* <applet code= Lines width = 300 height = 200> </applet> */ public class Lines extends Applet public void paint(graphics g) g.drawline(0, 0, 100, 100); g.drawline(0, 100, 100, 0); g.drawline(40, 25, 250, 180); g.drawline(75, 90, 400, 400); g.drawline(20, 150, 400, 40); g.drawline(5, 290, 80, 19); Yes, An object variable can be passed to a method for e.g. The program below has method equals ( ) which accepts an object, it compares this parameter object with the owner object and if equal returns true else it returns false. 5. (b) 16

17 Prelim Question Paper Solution class Test int a, b; Test (int i, int j) a = i; b = j; / / return true if 0 is equal to the invoking object boolean equals (Test 0) if (0.a = = a && 0.b = = b) return true; else return false; class Passobj public static void main (string args [ ]) Test ob1 = new Test (100, 22); Test ob2 = new Test (100, 22); Test ob3 = new Test ( 1, 1); System.out.println ( ob1 = = ob2 : + ob1.equals (ob1)) System.out.println ( ob1 = = ob3 : +ob1.equal (ob3)); / / Object to the / / left is calling & passed object is to the right. OUTPUT ob1 = = ob2 : true ob: = = ob3 : False 5. (c) APPLET import Java.awt.*; import java.applet * ; public class Hellow extends Applet stirng str; public void int ( ) str = getparameter ( String ); if (Str = = null) str = Java str = Hellow + str; public void paint (Graphics g) g.drawstring (str, 10, 100); show status (str); [8 Marks] Html. <Html> 17

18 : T.Y. Diploma JP <Head> <title> welcome </ title> < / Head> <body> <applet code = Hellow.Class width = 400 Height = 200 > < param name = String value = Applet! > </ Applet > < / Body> < / Html> Explain the problem of inter thread or process communication. The resource should be used in discipline and not only in ME. explain wait ( ) with dg. explain notify ( ) with dg. [8 Marks] 6. (a) <apple code= ImageMenu width = 140 height = 180 hspace = 0 vspace = 0> <param name= img value= menu.jpg > <param name= urlprefix value= > <param name= urllist value= pressroom/pressromm.shtml+aboutus/aboutus.shtml+<param name= targetlist value= _self+_self+_self+_self+_self+_self > <param name= urlsuffix value= > </applet> [4 Marks] 6. (b) Step 1 : Step 2 : Step 3 : Step 4 : Step 1 : purpose: Suspend is indefinite and therefore you must resume the thread by using resume ( ). While sleep (int n) is for n msec, puts the thread to sleep for n msec. Step 2 : higher priority thread suspends the lower priority thread. While sleep (int n), is used or producing delay Step 3 : example. Step 4 : dg. [4 Marks] 6. (c) In Java, each thread is assigned a priority, which affects the order in which it is scheduled for running. If no priority is specified, then same priority is given to every thread. The threads of the same priority are given equal treatment by the Java schedules and, therefore, they share the processor on a first come. First serve basis. To set the priority of a thread, use the set priority ( ) method as follows: Thread Name.set Priority (int Number); The intnumber is an integer value to which the threads priority is set. The thread class defines several priority constants. MIN_PRIORITY = 1 NORM_PRIORITY = 5 MAX_PRIORITY = 10 The intnumber may assume one of these constants or any value between 1 and 10. The default setting is NORM PRIORITY. i) to convert lower case string to upper case class ChangeCase public static void main(string args[ ]) 6. (d) 18

19 Prelim Question Paper Solution 6. (e) String s= This is a test. ; System.out.println( Original: + s); String upper = s.touppercase( ); String lower = s.tolowercase( ); System.out.println( Uppercase: + upper); System.out.println( Lowercase: + lower); The output produced by the program is shown here: Original: This is a test. Uppercase: THIS IS A TEST. Lowercase: this is a test. ii) to compare two string clas SortString static String arr[ ] = Now, is, the, time, for ; public static void main(string args[ ]) for(int j = 0; j < arr.length; j++) for(int i = j + 1; i < arr.length; i++) if(arr[i].compareto(arr[j]) < 0) String t = arr[j]; arr[j] = arr[i]; arr[i] = t; System.out.println(arr[j]); The output of this program is the list of words: Now is the time for class Search public static void main (String args [ ]) throws IOException BufferedReader br = new BufferedReader (new InputStream Reader (System.in)); int a [ ] = 1, 2, 3, 4, 5, 6, 7, 8, 9,10; int k Flag = 0; System.out.println ( Enter the number to be searched in arrary ); try k = Integer.parse Int(br.readLine ( )); Catch (Number Format Exception e) System.out.println ( Invalid format ); for (i = 0; i < 10; i ++) 19

20 : T.Y. Diploma JP if (a[i] = = k) flag = 1; break ; if (flag = = 1) System.out.println ( The no + k + is at + i position ); else System.out.println ( No not Round ); [4 Marks] 20