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

Interview Questions and Answers - Order By Newest

Q31. Difference between Scanner and BufferedReader ? Which one is faster and Why ?

Ans. Scanner is used for parsing tokens from the contents of the stream while BufferedReader just reads the stream.

BufferedReader read files efficiently by using a buffer to avoid physical disk operations.

Buffer size of Scanner is usually smaller than the Buffered Writer.

BufferedReader is faster that Scanner as it just reads the Stream and doesn't Parse the tokens to read the stream into primitive data types.

Sample Code for Scanner

Sample Code for BufferedReader

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Q32. Which of the following is true ?

a. We can serialize static variables
b. We can serialize transient variables
c. We can serialize final variables
d. We can serialize instance methods

Ans. We can serialize final variables

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Q33. 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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Q34. 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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Q35. 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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Q36. 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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Q37. 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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Q38. What are the different types of log files you have come across ?

Logging

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

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Q39. 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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Q40. What is SAR file ?

IBM WCS

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

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Q41. 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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Q42. 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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Q43. 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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Q44. What is the use of Property files ?

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

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Q45. 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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Q46. 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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Q47. 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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Q48. How to see last 500 lines of a log or text file

Unix

Ans. tail -500 <FILE_NAME>

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Q49. Write code to read data from a file and write it to a file with 2 threads using the thread name content

Core Java

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Q50. 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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Q51. Does Java generate .class file for interfaces ?

Core Java

Ans. Yes

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Q52. Which jar files need to be included for using Hibernate ?

Hibernate

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

or you can download hibernate core with all dependencies.

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