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Q541. 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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Q542. 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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Q543. http protocol is by default ... ?

Ans. stateless

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Q544. 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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Q545. Which of the following is a canonical path ?

1. C:\directory\..\directory\file.txt
2. C:\directory\subDirectory1\directory\file.txt
3. \directory\file.txt

Ans. 2nd

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Q546. What will the following code print when executed on Windows ?

public static void main(String[] args){
String parent = null;
File file = new File("/file.txt");
System.out.println(file.getPath());
System.out.println(file.getAbsolutePath());
try {
System.out.println(file.getCanonicalPath());
} catch (IOException e) {
e.printStackTrace();
}
}

Ans. file.txtC:file.txtC:file.txt

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Q547. What will be the output of following code ?

public static void main(String[] args){
String child = null;
File file = new File("/folder", child);
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}

Ans. NullPointerException at line:File file = new File("/folder", child);

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Q548. What will be the output of following code, assuming that currently we are in c:Project ?

public static void main(String[] args){
String child = null;
File file = new File("../file.txt");
System.out.println(file.getPath());
System.out.println(file.getAbsolutePath());
try {
System.out.println(file.getCanonicalPath());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

Ans. ..file.txt
C:WorkspaceProject..file.txt
C:Workspacefile.txt

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Q549. Which is the abstract parent class of FileWriter ?

Ans. OutputStreamWriter

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Q550. Which class is used to read streams of characters from a file?

Ans. FileReader

Sample Code for FileReader

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Q551. Which class is used to read streams of raw bytes from a file?

Ans. FileInputStream

Sample Code for FileInputStream

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Q552. Which is the Parent class of FileInputStream ?

Ans. InputStream

Sample Code for InputStream

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Q553. 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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Q554. 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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Q555. Which exceptions should be handled with the following code ?

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

Ans. FileNotFoundException

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Q556. 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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Q557. 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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Q558. 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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Q559. Difference between Class Path and Build Path ?

Ans. The build path is used for building your application. It contains all of your source files and all Java libraries that are required to compile the application.

The classpath is used for executing the application. This includes all java classes and libraries that are needed to run the java application.

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Q560. 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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Q561. 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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Q562. 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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Q563. 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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Q564. 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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Q565. 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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Q566. 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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Q567. 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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Q568. 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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Q569. 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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Q570. Which methods of the Pattern class have equivalent methods in the String class?

Ans. split() and macthes()

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