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Q2911. What is a Cursor ?

Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

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Frequently asked to experienced developers. Recently asked in many US interviews.

Q2912. What is database deadlock ? How can we avoid them?

Ans. When multiple external resources are trying to access the DB locks and runs into cyclic wait, it may makes the DB unresponsive.

Deadlock can be avoided using variety of measures, Few listed below -

Can make a queue wherein we can verify and order the request to DB.

Less use of cursors as they lock the tables for long time.

Keeping the transaction smaller.

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Q2913. What are temp tables ?

Ans. These are the tables that are created temporarily and are deleted once the Stored Procedure is complete.

For example - we may like to pull some info from a table and then do some operations on that data and then store the output in final output table. We can store the intermediary values in a temp table and once we have final output with us, we can just delete it.

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Q2914. Why Web services use HTTP as the communication protocol ?

Ans. With the advent of Internet, HTTP is the most preferred way of communication. Most of the clients ( web thin client , web thick clients , mobile apps ) are designed to communicate using http only. Web Services using http makes them accessible from vast variety of client applications.

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Q2915. what will be the output of this code ?

public static void main(String[] args){
   StringBuffer s1=new StringBuffer("Buggy");
   test(s1);
   System.out.println(s1);
}

private static void test(StringBuffer s){
   s.append("Bread");
}

Ans. BuggyBread

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Q2916. what will be the output of this code ?

public static void main(String[] args)    {
   String s1=new String("Buggy");
   test(s1);
   System.out.println(s1);
}

private static void test(StringBuffer s){
   s.append("Bread");
}

Ans. Buggy

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Q2917. what will be the output of this code ?

public static void main(String[] args)    {
   StringBuffer s1=new StringBuffer("Buggy");
   test(s1);
   System.out.println(s1);
}

private static void test(StringBuffer s){
   s=new StringBuffer("Bread");
}

Ans. Buggy

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Q2918. what will be the output ?

class Animal {
public void eat() throws Exception {
}
}

class Dog2 extends Animal {
public void eat(){}
public static void main(){
Animal an = new Dog2();
an.eat();
}
}

Ans. Compile Time Error: Unhandled exception type Exception

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Q2919. What are advantages of using Servlets over CGI ?

Ans. Better Performance as Servlets doesn't require a separate process for a single request.

Servlets are platform independent as they are written in Java.

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Q2920. 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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Q2921. 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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Q2922. 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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Q2923. 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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Q2924. 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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Q2925. http protocol is by default ... ?

Ans. stateless

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Q2926. 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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Q2927. 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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Q2928. 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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Q2929. 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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Q2930. What will be the output of following code ?

public static void main(String[] args){
String name = null;
File file = new File("/folder", name);
System.out.print(file.exists());
}

Ans. NullPointerException

at line: "File file = new File("/folder", name);"

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Q2931. What will be the output of following code ?

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

Ans. It will create the file myfile.txt in the current directory.

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Q2932. 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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Q2933. 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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Q2934. Which is the abstract parent class of FileWriter ?

Ans. OutputStreamWriter

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Q2935. Which class is used to read streams of characters from a file?

Ans. FileReader

Sample Code for FileReader

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Q2936. Which class is used to read streams of raw bytes from a file?

Ans. FileInputStream

Sample Code for FileInputStream

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Q2937. Which is the Parent class of FileInputStream ?

Ans. InputStream

Sample Code for InputStream

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Q2938. 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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Q2939. 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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Q2940. Which exceptions should be handled with the following code ?

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

Ans. FileNotFoundException

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