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Q2161. Does SQL allow null values ? Can we use it within Where clause ?

Ans. Yes , we can have null values for columns in SQL. Null value represent that the columns value is unknown or haven't been filled. Yes, We can use it within where clause to get the rows with null values.

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Q2162. Can we add duplicate keys in a HashMap ? What will happen if we attempt to add duplicate values ?

Ans. No, We cannot have duplicate keys in HashMap. If we attempt to do so , the previous value for the key is overwritten.

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Q2163. What is the use of HTTPSession in relation to http protocol ?

Ans. http protocol on its own is stateless. So it helps in identifying the relationship between multiple stateless request as they come from a single source.

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Q2164. Why using cookie to store session info is a better idea than just using session info in the request ?

Ans. Session info in the request can be intercepted and hence a vulnerability. Cookie can be read and write by respective domain only and make sure that right session information is being passed by the client.

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Q2165. What are different types of cookies ?

Ans. Session cookies , which are deleted once the session is over.

Permanent cookies , which stays at client PC even if the session is disconnected.

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Q2166. http protocol is by default ... ?

Ans. stateless

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Q2167. Can finally block throw an exception ?

Ans. Yes. Methods invoked from within a finally block can throw an exception. Failure to catch and handle such exceptions results in the abrupt termination of the entire try block.

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Q2168. Can we have try and catch blocks within finally ?

Ans. Yes, if we have a cleanup code that might throw an exception in the finally block, then we can have a try-catch block

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Q2169. Which is the abstract parent class of FileWriter ?

Ans. OutputStreamWriter

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Q2170. Which class is used to read streams of raw bytes from a file?

Ans. FileInputStream

Sample Code for FileInputStream

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Q2171. Which is the Parent class of FileInputStream ?

Ans. InputStream

Sample Code for InputStream

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Q2172. Which of the following code is correct ?

a.

FileWriter fileWriter = new FileWriter("../file.txt");
File file = new File(fileWriter );
BufferedWriter bufferedOutputWriter = new BufferedWriter(fileWriter);

b.

BufferedWriter bufferedOutputWriter = new BufferedWriter("../file.txt");
File file = new File(bufferedOutputWriter );
FileWriter fileWriter = new FileWriter(file);

c.

File file = new File("../file.txt");
FileWriter fileWriter = new FileWriter(file);
BufferedWriter bufferedOutputWriter = new BufferedWriter(fileWriter);

d.

File file = new File("../file.txt");
BufferedWriter bufferedOutputWriter = new BufferedWriter(file);
FileWriter fileWriter = new FileWriter(bufferedOutputWriter );

Ans. c.

File file = new File("../file.txt");
FileWriter fileWriter = new FileWriter(file);
BufferedWriter bufferedOutputWriter = new BufferedWriter(fileWriter);

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Q2173. Which exception should be handled in the following code ?

File file = new File("../file.txt");
FileWriter fileWriter = new FileWriter(file);

Ans. IOException

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Q2174. Which exceptions should be handled with the following code ?

FileOutputStream fileOutputStream = new FileOutputStream(new File("newFile.txt"));

Ans. FileNotFoundException

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Q2175. Will this code compile fine ?

ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));

Ans. Yes.

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Q2176. What is the problem with this code ?

class BuggyBread1 {

private BuggyBread2 buggybread2;

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Ans. Though we are trying to serialize BuggyBread1 object but we haven't declared the class to implement Serializable.

This will throw java.io.NotSerializableException upon execution.

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Q2177. Will this code run fine if BuggyBread2 doesn't implement Serializable interface ?

class BuggyBread1 implements Serializable{
private BuggyBread2 buggybread2 = new BuggyBread2();

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Ans. No, It will throw java.io.NotSerializableException.

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Q2178. Will this code work fine if BuggyBread2 doesn't implement Serializable ?

class BuggyBread1 extends BuggyBread2 implements Serializable{
private int x = 5;

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Ans. Yes.

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Q2179. Can we compose the Parent Class object like this ?

class BuggyBread1 extends BuggyBread2 {

private BuggyBread2 buggybread2;

public static void main(String[] args){
buggybread2 = new BuggyBread2();
}
}

Ans. Yes.

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Q2180. Will this code Work ? If not , Why ?

java.util.Calendar c = new java.util.Calendar();

Ans. No. It gives the error "Cannot Instantiate the type Calendar". Calendar is an abstract class and hence Calendar object should be instantiated using Calendar.getInstance().

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Q2181. Is java.util.Date an abstract Class ? Is java.util.Calendar an abstract Class ?

Ans. Date is not a abstract class whereas Calendar is.

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Q2182. What will the following code print ?

java.util.Calendar c = java.util.Calendar.getInstance();
c.add(Calendar.MONTH, 5);
System.out.println(c.getTime());

Ans. Date and Time after 5 months from now.

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Q2183. Which of the following code is correct ?

a. DateFormat df = DateFormat.getInstance();
b. DateFormat df = DateFormat.getDateInstance();
c. DateFormat df = DateFormat.getInstance(DateFormat.FULL);
d. DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);

Ans. All except c are correct.

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Q2184. What is the use of parse method in DateFormat ?

Ans. It is used to parse String to get the Date Object with initialized date.

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Q2185. Which of the following is not a valid java.util.Locale initialization ?

a. new Locale ()
b. new Locale ( String language )
c. new Locale ( String language , String country )

Ans. a i.e new Locale()

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Q2186. Which of the following is not a valid NumberFormat initialization ?

a. NumberFormat.getInstance()
b. NumberFormat.getDateInstance()
c. NumberFormat.getCurrencyInstance()
d. NumberFormat.getNumberInstance()

Ans. b i.e NumberFormat.getDateInstance()

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Q2187. What will the following code print ?

public static void main(String[] args){
Integer i1 = new Integer("1");
Integer i2 = new Integer("2");
Integer i3 = Integer.valueOf("3");
int i4 = i1 + i2 + i3;
System.out.println(i4);
}

Ans. 6

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Q2188. Which of the following syntax are correct ?a. LinkedList<Integer> l=new LinkedList<int>();b. List<Integer> l=new LinkedList<int>();c. LinkedList<Integer> l=new LinkedList<Integer>();d. List<Integer> l = new LinkedList<Integer>();

Ans. All are correct.

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Q2189. Which of the following code is correct ?

a. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).parse(str);

b. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).format(str);

c. Date date = DateFormat.getDateInstance(DateFormat.LONG, Locale.US).parse(str);

Ans. c

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Q2190. What's wrong with this code ?

public static void main(String[] args) {
String regex = "(\\w+)*";
String s = "Java is a programming language.";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(s);
while (matcher.next()) {
System.out.println("The e-mail id is: " + matcher.group());
}
}

Ans. matcher.find() should have been used instead of matcher.next() within while.

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