Interview Questions and Answers for 'L' | Search Interview Question

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Q511. Does every class needs to have one non parameterized constructor ?

Ans. No. Every Class only needs to have one constructor - With parameters or without parameters. Compiler provides a default non parameterized constructor if no constructors is defined.

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Q512. Difference between throw and throws ?

Core Java

Ans. throw is used to explicitly throw an exception especially custom exceptions, whereas throws is used to declare that the method can throw an exception.

We cannot throw multiple exceptions using throw statement but we can declare that a method can throw multiple exceptions using throws and comma separator.

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Q513. What are the platforms supported by Java Programming Language?

Core Java

Ans. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX/Linux like HP-Unix, Sun Solaris, Redhat Linux, Ubuntu, CentOS, etc

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Q514. What is IDE ? List few Java IDE ?

Tool

Ans. IDE stands of Integrated Development Environment. Few Java IDE's are WSAD ( Websphhere Application Developer ) , RAD ( Rational Application Developer ) , Eclipse and Netbeans.

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Q515. What is a Class ?

Core Java

Ans. A class is a blue print or Mold using which individual objects are created. A class can contain fields and methods to describe the behavior of an object.

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Q516. What data type Variable can be used in a switch statement ?

Core Java

Ans. Variables used in a switch statement can only be a byte, short, int, or char ( and String with Java 7 and above )

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Q517. What are the sub classes of Exception class?

Core Java

Ans. The Exception class has two main subclasses : IOException class and RuntimeException Class.

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Q518. How finally used under Exception Handling?

Core Java

Ans. The finally keyword is used to create a block of code that follows a try block. A finally block of code always executes, whether or not an exception has occurred.

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Q519. Explain Set Interface?

Core Java

Ans. It is a collection of element which cannot contain duplicate elements. The Set interface contains only methods inherited from Collection and adds the restriction that duplicate elements are prohibited.

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Q520. 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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Q521. What are use cases?

Process

Ans. It is part of the analysis of a program and describes a situation that a program might encounter and what behavior the program should exhibit in that circumstance.

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Q522. What is the difference between a break statement and a continue statement?

Core Java

Ans. Break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.

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Q523. 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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Q524. Variable of the boolean type is automatically initialized as?

Core Java

Ans. The default value of the boolean type is false.

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Q525. What is the Locale class?

Ans. The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region

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Q526. What environment variables do I need to set on my machine in order to be able to run Java programs?

Ans. CLASSPATH and PATH are the two variables.

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Q527. What is the difference between the size and capacity of a Vector?

Core Java

Ans. The size is the number of elements actually stored in the vector, while capacity is the maximum number of elements it can store at a given instance of time.

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Q528. What is the best practice configuration usage for files - pom.xml or settings.xml ?

Maven

Ans. The best practice guideline between settings.xml and pom.xml is that configurations in settings.xml must be specific to the current user and that pom.xml configurations are specific to the project.

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Q529. In a case where there are no instance variables what does the default constructor initialize?

Core Java

Ans. Java expects the superclass ( Object Class ) constructor to be called while creation of any object. So super constructor is called in case there are no instance variables to initialize.

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Q530. How can I change the default location of the generated jar when I command "mvn package"?

Maven

Ans. By default, the location of the generated jar is in ${project.build.directory} or in your target directory. We can change this by configuring the outputDirectory of maven-jar-plugin.

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Q531. How do I determine which POM contains missing transitive dependency?

Maven

Ans. run mvn -X

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Q532. Difference between Encapsulation and Data Hiding ?

Ans. Data Hiding is a broader concept. Encapsulation is a OOP's centri concept which is a way of data hiding in OOP's.

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Q533. Difference between Abstraction and Implementation hiding ?

Ans. Implementation Hiding is a broader concept. Abstraction is a way of implementation hiding in OOP's.

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Q534. How do you check memory leak in Java?

Core Java

Ans. You need to capture heap dump when it's in the healthy state. Start your application. Let it take real traffic for 10 minutes. At this point, capture heap dump. Heap Dump is basically the snapshot of your memory. It contains all objects that are residing in the memory, values stored in those objects, inbound

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Q535. Write a program to print the index of the first non repeated character in a java string

Core Java

Ans. public class BuggyBread1{
public static void main (String args[]) {
   String str = "hheello world";
   char[] charArray = str.toCharArray();
   char selectedChar = 'a';
   for(char char1: charArray){
      if(!str.contains(Character.toString(char1).concat(Character.toString(char1)))){
         selectedChar = char1;
         break;
      }
   }
   System.out.println(str.indexOf(Character.toString(selectedChar)));
}
}

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Q536. Which String class methods are used to make string upper case or lower case?

Core Java

Ans. toUpperCase and toLowerCase

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Q537. How to convert String to byte array and vice versa?

Core Java

Ans. We can use String getBytes() method to convert String to byte array and we can use String constructor new String(byte[] arr) to convert byte array to String.

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Q538. public class a {
   public static void main(String args[]){
      final String s1=""job"";
      final String s2=""seeker"";
      String s3=s1.concat(s2);
      String s4=""jobseeker"";
      System.out.println(s3==s4); // Output 1
      System.out.println(s3.hashCode()==s4.hashCode()); Output 2
   }
}

What will be the Output 1 and Output 2 ?

Core Java

Ans. S3 and S4 are pointing to different memory location and hence Output 1 will be false.

Hash code is generated to be used as hash key in some of the collections in Java and is calculated using string characters and its length. As they both are same string literals, and hence their hashcode is same.Output 2 will be true.

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Q539. What is the use of HashCode in objects ?

Core Java

Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc.

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Q540. Will finally be called always if all code has been kept in try block ?

Core Java

Ans. The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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