Interview Questions and Answers for 'T' | Search Interview Question

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Q1151. What does the web status code 404,500 and 200 mean ?

Ans. 404 means the resource is not found on the server.The resource might not be deployed correctly.

500 means internal server error which means that resource was located but then it resulted in some exception or error.

200 means Ok.

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Q1152. If Project A is calling web service of project B and there are some changes in project B, Will Project A needs to be rebuilt ?

Maven

Ans. That depends if the interface for the resource in Project B gets changed. If only the internal implementation is changed, No change is required in Project A. Project A is not even required to be rebuilt.

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Q1153. What is Dirty read in Database Transactions ?

Database

Ans. A dirty read occurs when a transaction is allowed to read data from a row that has been modified by another running transaction but not yet committed.

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Q1154. Have you ever felt the need of keeping the constructor private ?

Design

Ans. Yes, When either we don't want an object to be created ( class having all static elements and hence not required ) or object to be created using a static method or static block. One such example could be a situation when we would like app to load objects at start up and we would like to restrict new object creation by any request.

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Usually asked with Questions related to Generics.

Q1155. What are Type Erasures in Java ?

Core Java

Ans. Type erasure applies to the use of generics. When generics are used, they're pre compiled into compile time checks and execution-time casts.

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Q1156. 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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Q1157. 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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Q1158. How can one determine if JVM is 32-bit or 64-bit from Java Program ?

Core Java

Ans. There is a Java system property "sun.arch.data.model" that can tell if JVM is 32 bit of 64 bit

System.getProperty("sun.arch.data.model") can be used to get that property.

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Q1159. How can we find the memory usage of JVM from Java code?

Core Java

Ans. Using Runtime object.

Runtime runtime = Runtime.getRuntime();

runtime.totalMemory();
runtime.freeMemory();

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Q1160. How can we catch an exception thrown by another thread ?

Core Java

Ans. http://stackoverflow.com/a/6548203/2789764

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Q1161. Why calculations in float or Double sometimes gives unpredictable results ?

Core Java

Ans. Because the way float values are stored its not precise.

For example - 0.1 is actually stored as
0.1000000000000000055511151231257827021181583404541015625

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Q1162. What different level of logging you use while coding ?

Logging

Ans. I use trace for debugging purpose. Info for displaying some important info, thought its rare as we have enabled info logging in production. Warn in case something went wrong but we still resume the flow in spite of it or have take alternate flow as its expected sometimes. Error logging in case it was completely unexpected and mostly when it breaks the flow.

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Q1163. Explain Travelling SalesMan Problem ?

Algorithm

Ans. https://en.wikipedia.org/wiki/Travelling_salesman_problem

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Q1164. What is the use of @Before annotation ?

Junit

Ans. When executing tests it is common that multiple tests need similar objects to be created before they can run. @before specifies a method that provide that initialization for the set of Unit Tests.

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Q1165. What is Java NumberFormatException ?

Core Java

Ans. NumberFormatException is the exception that Java throws when we try to convert one data type to the Number data type but the value is not parsable to be a Number.

For example , the following code will result in the NumberFormatException

String string = "Buggy";
int strtoInt = Integer.parseInt(string);

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Q1166. Write a Java Program to check Armstrong Number ?

Core Java

Ans. http://www.programmingsimplified.com/java/source-code/java-program-armstrong-number

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Q1167. How Spliterator in Java 8 different than iterator ?

Core Java

Ans. Though there are many differences the way internally they both iterates the collections and streams respectively, but the main difference in performance that is achieved by spliterator as it can iterate Streams in Parallel whereas iterator only iterates collections sequentially.

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Q1168. Which is better in terms of performance - Iterator or Spliterator ?

Core Java

Ans. Spliterator has better performance potential than iterators but only if the potential is used. Spliterator can iterate streams in parallel as well as in sequence whereas iterator can only iterate in sequence.

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Q1169. Difference between System.out.printf and System.out.println ?

Core Java

Ans. println prints an additional end of line whereas printf doesnt.

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Q1170. What is the use of return statement without any argument ?

Core Java

Ans. Such return is only expected in methods that returns void. the purpose of having return in such a method is to return the flow out of method and return to the place where it was called. Its actually used to prematurely return the control from the method.

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Q1171. Does it make sense to have return statement at the end of method ?

Core Java

Ans. It make sense if its returning something. It doesnt make sense for void methods where return statement is not preceded by anything. In case of void methods , return as last statement has no impact and is actually a overhead.

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Q1172. How to specify the or/and combination restrictions within Criteria in Hibernate ?

Hibernate

Ans. session.createCriteria(Employee.class).add( Restrictions.or(Restrictions.like("name", "A%"),Restrictions.like("name", "B%"))).list();

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Q1173. Difference between Maven Project and Module ?

Maven

Ans. Maven Module has a Parent whereas Project doesnt. when we add the parent section to the pom file, it adds the module section to the parent project pom file. When we execute mvn compile / install, it basically checks that module section of the parent to identify all the modules that needs to be compiled first.

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Q1174. What is meant by following error ?

Source folder is not on the Java build class path

Core Java

Ans. It means that the respective folder is not looked upon by Java to look for java or resource files and hence not being included as part of build.It needs to be added to Java Build Path.

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Q1175. What is the use of .project file in eclipse ?

Tool

Ans. .project is a project description file that helps plugins and eclipse understand about the project - organization of projects , their names, builders used by them etc.

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Q1176. What is a .classpath file in eclipse ?

Tool

Ans. .classpath specifies the source java and resource folders that are used by Builders to build.

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Q1177. What is a shutdown hook ?

Core Java

Ans. Shutdown hook is a thread that is invoked implicitly by JVM just before the shut down. It is used to clean up unused resources.

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Q1178. Can we start the same thread twice ?

Core Java

Ans. No we cannot start the same thread twice. Each thread has a lifecycle.

But Yes, we can run the same code in parallel using different threads.

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Q1179. Write an Algorithm for Graph Traversal ? The Graph has a loop.

Algorithm

Ans. Please not that all such questions can be easily answered through recursion.

Simple recursive implementation could be

traverse(root);

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
System.out.println(element);
}
}

but this algo / code lead to endless loop if there is a loop in graph traversal.

So you can keep a collection to keep track of which elements have laready been traversed

static List<Elements> listOfAlreadyTraversedElements = new ArrayList<Elements>();

main(){
traverse(root);
}

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
listOfAlreadyTraversedElements.add(element);
System.out.println(element);
}
}

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Q1180. How is String class unique ?

Core Java

Ans. String class is immutable as well as final. Because of these properties , String objects offer many benefits

1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesnt create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence its not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

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