127 Std 12 Viva Question Answers

INFORMATICS PRACTICES – VIVA QUESTIONS – STD 12

1. Differentiate between getText() and setText(). getText()-Used getText()-Used to retrieve text. setText()-Used setText()-Used to set the text. 2. Differentiate between TextField and TextArea. Text Area-Accepts Multiple Lines of Data Text Field-Accepts Single Line of Data 3. What is meant by a ternary operator? Consists of 3 Operands - ? : 4. What is meant by Integer.parseInt? Integer.parseInt Integer.parseInt is used to convert string value to integer value. 5. What property has to be added to get color on a label? Opaque property has to be added to get color on a label. 6. What is the difference between isSelected() and setSelected()? isSelected – isSelected – returns returns true if the component is selected. setSelected – setSelected – sets sets the component as selected, if set to true, default is false 7. What is the difference between getSelectedIndex() and getSelectedItem()? getSelectedItem()? getSelectedIndex – getSelectedIndex – retrieves retrieves the index of the selected item getSelectedItem – getSelectedItem – retrieves retrieves the selected item 8. How the items in a jList can be added? The items can be added to a jList by the way of model property 9. What is the purpose of using break statement? Break statement terminates the current loop. 10.What 10.What is a button group? Button group is an invisible component by which the user can select one option from multiple choices and all the options comes under one group – eg. Radiobutton, Checkbox etc. 1


11.What is the difference between jRadioButton and jCheckBox? jRadioButton is commonly used to select one option out of many choices jCheckBox can be used to select all the options at a time 12.Explain event handler? It is used to handle different types of events. Example: action performed, focus lost, key pressed etc. 13.Explain the event – state changed? The event state changed for the specified component is subjected to change during the run time. Like being Selected or Deselected 14.What are the advantages of applying menus in java? It occupies less space, easily understandable 15.What does the trim method will do? The trim function is used to remove leading and trailing spaces for the given text. 16.What for length () method is used? It returns the number of characters for the given string. 17. What is the difference between Integer.parseInt and Integer.toString? Integer.parseInt – is used to convert string value to integer value. Integer.toString – is used to convert integer value to string. 18.What is the difference between string and string buffer? String-They are mutable .Once created cannot be changed, if any change occurs the original remains unchanged and new string will be created with the changed name. String Buffer- These are immutable. These can be changed or modified according to the user. 19.What property has to be implemented in the list for accessing the list controls? 2


The list must be given a custom code(new DefaultListModel) in their model properties. 20.What is the difference between getSelectedValue() and getSelectedIndex()? getSelectedValue()-Returns the value when single item is selected, if multiple items are selected then returns the first selected value. getSelectedIndex()-Returns the index of the selected item. 21.What is the purpose of using Default List Model ? It is the default implementation of list model which offers methods for manipulating list elements. 22.State the difference between getModel and setModel. getModel()-Used to retrieve the model of the given component. setModel()-Used to set the model of the component. 23.Explain about JOptionPane. What are the different methods that can be u sed along with it? JoptionPane is an Abstract Class in java for which there is no requirement of objects. Different Methods with JoptionPane are-showMessageDialog, showConfirmDialog, showInputDialog 24.Explain about jPanel. Jpanel is a Middle Level Container. It can hold various components within it. It is a parent component of Swing Containers. 25.Explain about Java Math class. It consists of various in built methods used for performing mathematical operations like rounding of the decimal places, adding the amounts, removing the decimal places etc. 26.Explain the methods that are used along with math objects. round(double a)-used to round off the given value to the nearest number truncate(double a,int b)-removes the decimal places 27.Explain about String Buffer class. 3


String buffer classes are mutable. These can be changed or modified according to the user. 28.Explain the methods that are used along with string buffer. reverse()-used to reverse the given string length()-retrieves the number of characters of the given String insert()-used to insert a new string with the previous String 29.What is meant by a class? Class is used to encapsulate data and methods together in a single unit. 30.What has to be carried out in the jTable model properties? The table settings (column details) have to be given. The number of rows has to be set to Zero. 31.What does the addRow method does? addRow method is used to add a new row to the table 32.Explain about getSelectedRow() and getRowCount()? getSelectedRow()-Returns the selected row from the table getRowCount()-Returns the total number of rows in the table 33.What does removeRow() method does? Used to remove the selected row from the table 34.What does getValueAt() method does? Used to return the cell values for the rows and columns 35.Explain about call by value and call by reference? Call by value-Uses variables to interchange the values Call by Reference-Uses Jframe to interchange the values 36.In the given statement, public class callby extends javax.swing.JFrame, which is the super class and which is the sub class? Super class-javax.swing.Jframe Sub Class-name given for the Jframe Form (callby) acts as the sub class 4


37. What is the difference between combo box and a list box? Combo Box- Allows only single selection List Box- Allows multiple selections 38. What does getSelectedIndex()==0 denotes? This denotes that the first index is selected 39.What is the difference between do while loop, while loop and for loop? Do while loop-exit controlled loop Test expression is tested at the end of the loop. While loop-entry controlled loop Test Expression is tested at the beginning of the loop For loop- Initialization expression, Text Expression, Increment/Decrement Expression, Body of the loop 40.State any two methods that can be associated with each of jLabel, jButton, jTextField, jCombo Box, jRadio Button, jTextArea, jCheckBox, jList, JOptionPane. jLabel-getText(),SetText() jButton-setEnabled(), setVisible() jTextField-isEnabled(), setText() jComboBox-getSelectedItem, getSelectedIndex jRadioButton-isSelected(), setSelected() jTextArea-append, setText() jCheckBox-isSelected(), setSelected() jList-getSelectedValue(),isSelectedIndex() JoptionPane-showMessageDialog, ShowConfirmDialog 41. What is inheritance? What are the various forms that are used in it? Method of creating new class called Sub class from the main class(Super Class).Various Forms-Single Inheritance, Multiple Inheritance, MultiLevel Inheritance, Hierarchical and Hybrid. 42.Define polymorphism. Give examples. 5


It is the ability of a method that can be executed in many forms. Example-operator overloading and method overloading 43. What is the importance of abstract class in java? The class for which it is not essential to declare objects is called abstract class. Example-JoptionPane, Jframe.Since they do not require objects they are used as base Class. 44. What is a front end? The application provides some form using which the user enter data is called the front end. 45.What is a back end? The application which usually stores a lot of data in the form of database is called back end. 46.What is JDBC? Java Database Connectivity is used to establish connectivity between java and the databases. 47.What are the basic class libraries that are required in the application for data connectivity? How to add these libraries into our application? The basic class libraries are Driver manager class, Connection class, Statement class. These can be added by importing it into our application. 48.Why forName() method is used? forname()-used to load the Driver Class 49.What is data validation? It is the process of ensure that a program operates on clean, correct and useful data. 50.What is the purpose of using isEmpty() method? isEmply()-used to check if any of the component is empty

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51. What for class.forName method is instantiated? Instantiated to connect database Server with JDBC 52.Explain the given statement - Connection con=(Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/details","root"," mysql123" . The getConnection() is used to establish the connection to the database. 53. Explain the following command : Statement stmt=(Statement) con.createStatement(); It is used to create a statement stmt from the connection object by using createStatement() method. It is used to send and execute SQL statements. 54.Explain the given command : String query="INSERT INTO dept VALUES (' "+name+" ',' "+age+" ',' "+gender+" ',' "+dept+" ',' "+location+" ');"; A variable query with string type is created to initialize SQL statement and this statement is used to add values into the mysql table. 55.Explain the given statement : stmt.executeUpdate(query); Executes the SQL statement stored in query by using executeUpdate() method. 56. Identify the object name, class name and method name used in the given statement : ResultSet rs= stmt.executeQuery(query); Class-ResultSet Object-rs Method-executeQuery() 57.What does the rs.next() method does? Used to move to the next record in the database 58.Explain the methods getString() and getInt(). getString()-used to retrieve the String values from the database getInt()-used to retrieve the integer values from the database. 59.Explain the usage of the following methods : rs.close(), stmt.close(), con.close(). 7


These methods are used to close all the operations of result set, statement, connection. 60.What are the DDL commands? These are commands which are used to create, destroy or restructure databases and tables. DDL commands are – CREATE, DROP, ALTER 61.What are the DML commands? These are commands which are used to manipulate data within tables. DML commands are – INSERT, UPDATE, DELETE. 62. Name the clauses that can be used along with SELECT command. DISTINCT, WHERE, BETWEEN, IN, LIKE, IS NULL/ NOT NULL, ORDER BY, GROUP BY, HAVING, UNION

63.Explain the numeric functions with example. Numeric functions perform operations on numeric values and return numeric values. Numeric functions are – ROUND, POWER, TRUNCATE

64.What for concat() function is used? It is used to join or combine two or more strings. 65.What is the difference between instr() and substring() function? INSTR – returns the position of the first occurrence of the given string. SUBSTRING or MID – returns the specified number of characters from the middle. 66.Define aggregate functions. Give examples. They work on multiple values to return a single value. Example-sum(),avg(),min(),max() 67.What is the difference between where clause and having? Where clause is used to put a condition on a individual row in a select statement. Having is used to put a condition on individual group formed by group by clause in a select statement 68.What is the purpose of using group by? 8


Group by clause is used in select statement in conjunction with aggregate functions to group the results based on distinct values 69.Define primary key and candidate key. Primary key-used to uniquely identify each row Candidate key-a column or a group of columns which can be used as the primary key 70.What is the purpose of using UNION in SELECT statement? Union is used to combine two select statements 71.What is the difference between cross join and equi join? Cross join-obtained by pairing each row of one table with each row of other. Equi join-obtained by putting equality condition on cartesian product of two tables. 72.What is the difference between DROP and DELETE? Drop-used to drop the entire table Delete-used to delete individual record from the table 73.Define a transaction. The unit of work that has to be done in a logical order and successfully as a group or not done at all. 74.What is the difference between commit and rollback? Commit is used to save all the changes made to the database. It is issued at a time when the transaction is complete and all the changes have been successful and needed to be saved to database. Ex-Commit work; Roll back cancels the entire transaction. It rolls the transaction to the beginning. It aborts the changes made to the transaction. Ex-Rollback work; 75. JFrame contains several pane. To what pane are the components added? 76.Which property would you set for setting the password as „@‟ ?

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77.What is the difference between action performed and key typed? 78.Difference between OL and UL tag. 79.What is a component? 80.What is inheritance? Give an example by the way of source code. 81.State any 2 methods in math class which does not take parameters. 82.State any 2 methods in String class which does not take parameters. 83.String a =jTF1.getText(). Explain the entire statement. 84.JComboBox1.getSelectedItem(). What will be the return type for the method? 85.What is concrete class? Give one example. 86.If a column in a table is having a relation with another table, then the column is called as what? 87.What will be the values that can be applied along with aggregate functions? 88.State the languages that are supported by procedural programming. 89.Which package is added to the JFrame automatically? 90.What is a foreign key? 91.Give an example for save point. 92.Write a query using union all. 93.What is data encapsulation? 10


94.Difference between int and Integer. 95. How does x.equals() is different from x= =? 96. Explain about commit and rollback. 97. When creating a table if the primary key constraint is not added, can it be added later? If so, specify the query? 98. Mention any two native classes that are supported by java. 99. Which keyword in java is used to many any variable as constant? 100. What is a dialog? State any 2 methods that can be used along with JOptionPane. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117.

Define GUI. What is a component? Define a method. What is an event? What is a Boolean datatype? Difference between getSelectedIndex and getSelectedItem. Difference between isSelected and setSelected. Methods of JOption Write the syntax and example for all the control statements. Difference between if and switch Difference between while and do while Difference between int and Integer Difference between int x and String x Define object oriented programming State the languages supported by object oriented programming Define procedural programming State the languages supported by procedural programming

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118. State the languages supported by object oriented as well as procedural programming. 119. Difference between procedural programming and object oriented programming. 120. Define class. 121. Define object. 122. What is meant by data encapsulation? 123. What is meant by data abstraction? 124. Give example for data member. 125. Define polymorphism. 126. Explain the types of polymorphism with a suitable example. 127. How method can be overloaded? Give example. 128. What is an abstract class? Give example. 129. What is a concrete class? Give example. 130. What is an inheritance? Give one example by the way of source code. 131. What are the methods that are used in math class? 132. What are the methods that are used in string class? 133. State any 2 methods in math class that do not take parameters. 134. State any 2 methods in string class that do not take parameters. 135. It is not necessary to import any package for the math class. Why? 136. State any 2 conversion methods 137. What are the different levels of containers in java? 138. Difference between action performed and caretupdate. 139. Mention any 4 native classes of java. 140. Which package is added to the jFrame by default? 141. Which keyword is used to make a variable constant? 142. For(int x=1; ; x++) is there any error with the given statement or what will be the output? 143. Whether, if(a= =” ”) is equal to if(a= = null) ? 144. I am in the source window, now I want to add a component, but I couldn‟t get the palette window. Why? 145. jFrame contains several pane. To which pane are the components added? 146. Which property would you set for setting the password character as „%‟? 12


147. Difference between OL and UL tag? 148. jList1.isSelected( ), what will be the return type for method? 149. Is there any difference between a jRadioButton and a jCheckBox initially? 150. Which keyword is used to inherit data members and methods of the base class and allows the derived class to use it? 151. Which package is added to the jFrame automatically? 152. Difference between seticon and icon property. 153. Difference between system.exit and dispose. 154. Any three non printable characters other than “\n”. 155. What is meant by type conversion? 156. What are the different types of access specifiers ? Explain. 157. What are the basic libraries that are required to work with database connectivity? 158. What is jdbc api? 159. Can you insert or remove rows from an existing jTable? 160. Which property is used to give color to a label? 161. Which property is used to change the choices displayed in a list? 162. Which property is used to change the selection 163. Which component of a swing window lets you to create a general dialog? 164. What is meant by data validation? State any one method related to data validation. 165. What is meant by open source software? 166. How open source software different from proprietary software? 167. What is UNICODE? 168. Difference between ASCII and ISCII. 169. What is meant by degree and cardinality? 170. Explain DML and DDL. 171. What is a relation? 172. Difference between tuple and attribute. 173. What is meant by referential integrity? Give one example. 174. Explain numeric function and its types in detail. 175. Explain string function and its types in detail. 176. Explain date and time function and its types in detail. 13


177. What is meant by aggregate function? 178. What are the datatypes that can be applied along with aggregate functions? 179. Explain equi join and cross join. 180. How null values are treated along with aggregate functions? 181. Difference between having and where. 182. Difference between orderby and groupby. 183. Give one example for union and union all. 184. Explain about the various constraints in mysql. 185. Define a transaction. 186. What is meant by rollback and commit? 187. If a column in a table is having a relation with another table, then how the column can be referred? 188. Define savepoint. Give one example. 189. What are primitive datatypes? 190. What are reference datatypes? 191. What is the difference between System.exit(0) , dispose( ) ? 192. What is meant by fall through? 193. What is the difference between break and continue? 194. Name two classes to be imported for JDBC. 195. Write the range of short and int datatypes. 196. Write the statement i) to convert a String S to an integer N ii) to convert a double B to an integer A. 197. What does the catch block do? 198. Define constraints. 199. State two important properties of JCombobox. 200. Explain the syntax of the import statement. 201. Explain src and align attribute of the image tag. 202. Differentiate between html and xml. 203. Which component of swing window let you create a general purpose dialog? 204. How do you prevent a subclass from having access to a member of super class? 205. What is void? Give example. 14


206. What is a constructor? What are its types? 207. What is return? Give example. 208. Why xml called as meta language? 209. What is the difference between and tags? 210. What happens when autocommit is set on?

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127 Std 12 Viva Question Answers

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