Core Java - Interview Questions and Answers for 'File' | Search Interview Question

Core Java - Interview Questions and Answers for 'File' - 52 question(s) found - Order By Rating

Q1. Which jar files need to be included for using Hibernate ?

Ans. hibernate-orm
hibernate-validator
hibernate-ogm
hibernate-search

or you can download hibernate core with all dependencies.

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Q2. Does Java generate .class file for interfaces ?

Core Java

Ans. Yes

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Q3. Write code to create a folder if it doesn't exist.

Core Java

Ans. File folder = new File(path);

if(!folder.exists()){
try {
folder.mkdir();

} catch (Exception e) {}
}

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Q4. How does encoding affect using Reader / writer classes or Stream classes in Java ?

Core Java

Ans. Which group of bytes represent which character is defined by character encoding. So when reading character by character from a stream of bytes using Reader, specifying character encoding becomes significant as the same group of bytes can represent different character in different character encoding(Eg UTF-8 and UTF-16 etc.)

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Q5. Write code to read data from a file and write it to a file with 2 threads using the thread name content

Core Java

^{This question was recently asked at 'verifone'.This question is still unanswered. Can you please provide an answer.}

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Q6. How to see last 500 lines of a log or text file

Unix

Ans. tail -500 <FILE_NAME>

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Q7. In a file there are 1 million words . Find 10 most frequent words in that file.

Design

^{This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.}

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Q8. As root, if you have to assign the owner for the file and set only read permission for the owner, Write a unix command to do it.

Unix

Ans. chmod 477

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Q9. What are the different types of log files you have come across ?

Logging

Ans. error , access , authentication , message , database etc

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Q10. What is a host file ?

Operating System

Ans. It's an operating system file that maps IP address to host names. The hosts file assists the OS in addressing networked components and serves the function of translating human friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network.

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Q11. What are the ways in which an application can maintain config variables ?

Ans. 1. Property files
2. config xml
3. Database

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Q12. What is the use of Property files ?

Ans. Property files are used to maintain configurable values as key value pairs.

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Q13. What is the difference between RollingFile and RollingRandomAccessFile in log4j ?

Log4j

^{This question is still unanswered. Can you please provide an answer.}

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Q14. What is ACL ?

Operating System

Ans. Access Control List or ACL is the list of permissions attached to an object in the File System.

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Q15. Why is it important to close files and streams ?

Core Java

Ans. Optimizing Resource utilization. When you open a file using any programming language , that is actually a request to operating system to access the file. When such a request is made , resources are allocated by the OS. When you gracefully close those files, those resources are set free.

In Java if you don’t close the streams and files, Garbage collection identifies the open files which have lost the reference and hence will close them.

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Q16. What is SAR file ?

IBM WCS

Ans. Its the Store Archive that holds the store Assets in the compressed form.

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Q17. Upon compiling the following class, What .class files will get created

public class OuterClass{
class InnerClass{
}
}

Core Java

Ans. OuterClass.class AND OuterClass$InnerClass.class

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Q18. Given two files with list of words, write a program to show the common words in both files

Core Java

Ans. import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.io.*;
public class Common {
public static void main(String ar[])throws Exception
   {
      File f=new File("a.txt");
File f1=new File("x.java");
      System.out.println(f.exists());
FileInputStream fin = new FileInputStream(f);
      FileInputStream fin1 = new FileInputStream(f1);

      byte b[]=new byte[10000];
byte b1[]=new byte[10000];
fin.read(b);
fin1.read(b1);
String s1 = new String(b);
String s2 =new String(b1);

String words1[] = s1.trim().split(" ");
String words2[] = s2.trim().split(" ");
Listlist1 = new ArrayList<>(Arrays.asList(words1));
Listlist2 = new ArrayList<>(Arrays.asList(words2));
list1.retainAll(list2);
System.out.println(list1);
}
}

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Q19. What is the difference between

File f = new File("homexyz.txt");

and

File f = File.createTempFile("xyz",".txt","home"); ?

Core Java

Ans. First will not create physical file in storage whereas the second will.

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Q20. How to specify the sequence in which sub modules needs to be built ?

Maven

Ans. By specifying the modules in the same sequence in the parent pom.

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Q21. Watching a directory for changes. Monitoring a directory.

Core Java

Ans. http://www.logicbig.com/tutorials/core-java-tutorial/java-nio/java-watch-service/

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Q22. Have you ever tried compressing data using Java ?

Core Java

Ans. Yes, we can use ZipInputStream class for compressing the FileInputstream object.

Sample Code for ZipInputStream

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Q23. How and when the Buffer is cleared when using Buffered Writer Classes ?

Core Java

Ans. Buffer is cleared in 2 circumstances, i.e 1. naturally when the buffer is filled and 2. explicitly when the method flush is called ( for flushing the residual )

Ideally we just need to call flush once at the end of file writing so that the residual content should be dumped to file.

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Q24. Tell something about BufferedWriter ? What are flush() and close() used for ?

Ans. BufferedWriter is temporary source for data storage.BufferedWriter is used to write character data to the file.Flush() is method available in B.W which ensures that all data items are written to file including last character.Close() is used to closes the character output stream.

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Q25. What is Scanner class used for ? when was it introduced in Java ?

Core Java

Ans. Scanner class introduced in Java 1.5 for reading Data Stream from the imput device. Previously we used to write code to read a input using DataInputStream. After reading the stream , we can convert into respective data type using in.next() as String ,in.nextInt() as integer, in.nextDouble() as Double etc

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Q26. What is Spring configuration file?

Spring

Ans. Spring configuration file is an XML file. This file contains the classes information and describes how these classes are configured and introduced to each other.

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Q27. What is a stream and what are the types of Streams and classes of the Streams?

Core Java

Ans. A Stream is an abstraction that either produces or consumes information. There are two types of Streams :

Byte Streams: Provide a convenient means for handling input and output of bytes.

Character Streams: Provide a convenient means for handling input & output of characters.

Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream.

Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.

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Q28. What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

Core Java

Ans. The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented

Sample Code for InputStream

Sample Code for OutputStream

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Q29. What is the purpose of the System class?

Core Java

Ans. The purpose of the System class is to provide access to system resources.

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Q30. 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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