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 Q261. Difference between socket and servlet ?Java EE
Ans. servlet is a small, server-resident program that typically runs automatically in response to user input.
A network socket is an endpoint of an inter-process communication flow across a computer network.

We can think of it as a difference between door and gate. They are similar as they both are entry points but they are different as they are put up at different areas.

Sockets are for low-level network communication whereas Servlets are for implementing websites and web services

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   Like         Discuss         Correct / Improve     java   j2ee   networking   servlet   socket   difference between.java.net   technologies   architecture

 Q262. What is PermGen or Permanent Generation ?Core Java
Ans. The memory pool containing all the reflective data of the java virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas. The Permanent generation contains metadata required by the JVM to describe the classes and methods used in the application. The permanent generation is populated by the JVM at runtime based on classes in use by the application. In addition, Java SE library classes and methods may be stored here.

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   Like         Discuss         Correct / Improve     java   jvm   memory management   permgen   permanent generation   advanced   architecture     Asked in 9 Companies      expert

 Q263. What is metaspace ?Core Java
Ans. The Permanent Generation (PermGen) space has completely been removed and is kind of replaced by a new space called Metaspace. The consequences of the PermGen removal is that obviously the PermSize and MaxPermSize JVM arguments are ignored and you will never get a java.lang.OutOfMemoryError: PermGen error.

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  Q264. Advantage of Collection classes over Arrays ?Core Java
Ans. Collections are re-sizable in nature. We can increase or decrease the size as per recruitment.
Collections can hold both homogeneous and heterogeneous data's.
Every collection follows some standard data structures.
Collection provides many useful built in methods for traversing,sorting and search.

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   Like         Discuss         Correct / Improve     java   collections   collections classes   advantages of collections over arrays   collections vs arrays   basic interview question     Asked in 6 Companies      basic        frequent

 Q265. Can we call constructor explicitly ?
Ans. Yes.

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   Like         Discuss         Correct / Improve     java   constructor   constructor chaining   oops   call constructor explicitly   yes-no
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 Q266. Does a class inherit the constructor of its super class?
Ans. No.

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   Like         Discuss         Correct / Improve     java   oops   constructor   inheritence   constructor inheritance   yes no

 Q267. What is the difference between float and double?
Ans. Float can represent up to 7 digits accurately after decimal point, where as double can represent up to 15 digits accurately after decimal point.

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 Q268. Is it possible to compile and run a Java program without writing main( ) method?
Ans. Yes, it is possible by using a static block in the Java program.

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 Q269. Do you think that Java should have had pointers ?Core Java
Ans. Open ended Questions.

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   Like         Discuss         Correct / Improve     java   open questions   pointers   advanced

 Q270. Tell something about history of Java ?Core Java
Ans. Java was initially found in 1991 by James Gosling, Sun Micro Systems. At first it was called as "Oak". In 1995 then it was later renamed to "Java". java is a originally a platform independent language. Currently Oracle, America owns Java.

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 Q271. How to find if JVM is 32 or 64 bit from Java program. ?
Core Java
Ans. You can find JVM - 32 bit or 64 bit by using System.getProperty() from Java program.

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   Like         Discuss         Correct / Improve     java   jvm 32   jvm 64   jvm

 Q272. According to Java Operator precedence, which operator is considered to be with highest precedence?Core Java
Ans. Postfix operators i.e () [] . is at the highest precedence.

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  Q273. What is Comparable Interface?Core Java
Ans. It is used to sort collections and arrays of objects using the collections.sort() and java.utils. The objects of the class implementing the Comparable interface can be ordered.

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   Like         Discuss         Correct / Improve     java   collections   comparable interface     Asked in 7 Companies      intermediate        frequent
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 Q274. What is Externalizable interface?Core Java
Ans. Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism.

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   Like         Discuss         Correct / Improve     java   serialization   externalizable interface     Asked in 2 Companies      intermediate        rare

 Q275. What are the features of encapsulation ?Core Java
Ans. Combine the data of our application and its manipulation at one place.

Encapsulation Allow the state of an object to be accessed and modified through behaviors.

Reduce the coupling of modules and increase the cohesion inside them.

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  Q276. Write a method to check if input String is Palindrome?Core Java
Ans. private static boolean isPalindrome(String str) {

if (str == null)
return false;

StringBuilder strBuilder = new StringBuilder(str);

strBuilder.reverse();

return strBuilder.toString().equals(str);

}

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   Like         Discuss         Correct / Improve     java   string   stringbuilder   stringbuilder   string class   code   palindrome     Asked in 38 Companies      Basic        frequent

 Q277. Write a method that will remove given character from the String?Core Java
Ans. 
private static String removeChar(String str, char c) {    

   if (str == null)        

      return null;     

   

   return str.replaceAll(Character.toString(c), "");

}


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   Like         Discuss         Correct / Improve     java   string   string class   code   write code

 Q278. Why String is popular HashMap key in Java?Core Java
Ans. Since String is immutable, its hashcode is cached at the time of creation and it doesnt need to be calculated again. This makes it a great candidate for key in a Map and its processing is fast than other HashMap key objects. This is why String is mostly used Object as HashMap keys.

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   Like         Discuss         Correct / Improve     java   string class   string   immutable  immutability   hashmap   immutable  immutability   hashcode   hash code   advanced     Asked in 2 Companies      expert        frequent

 Q279. What does String intern() method do?Core Java
Ans. intern() method keeps the string in an internal cache that is usually not garbage collected.

Moreover provide reference for scp object for corresponding string object present in heap memory.

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   Like         Discuss         Correct / Improve     java   string class   string   intern method   garbage collection   advanced     Asked in 2 Companies      expert

 Q280. Will the following program display ""Buggy Bread"" ?

class Test{
   static void display(){
      System.out.println(""Buggy Bread"");
   }
}

class Demo{
   public static void main(String... args){
      Test t = null;
      t.display();
   }
}		Core Java
Ans.  Yes. static method is not accessed by the instance of class. Either you call it by the class name or the reference.

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   Like         Discuss         Correct / Improve     java   static   static method   code

 Q281. How substring() method of String class create memory leaks?Core Java
Ans. substring method would build a new String object keeping a reference to the whole char array, to avoid copying it. Hence you can inadvertently keep a reference to a very big character array with just a one character string.

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Very frequently asked in HCL Tech ( Based of 4 inputs )
  Q282. Write a program to reverse a string iteratively and recursively ?Core Java
Ans. Using String method -

new StringBuffer(str).reverse().toString();

Iterative -

public static String getReverseString(String str){
StringBuffer strBuffer = new StringBuffer(str.length);
for(int counter=str.length -1 ; counter>=0;counter--){
strBuffer.append(str.charAt(counter));
}
return strBuffer;
}

Recursive -

public static String getReverseString(String str){
if(str.length <= 1){
return str;
}
return (getReverseString(str.subString(1)) + str.charAt(0);
}

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  Q283. Write a Program to check if 2 strings are Anagrams ?Core Java
Ans. public void checkIfAnagram(String str1,String str2){
boolean anagram = true;
for(char c:str1.toCharArray()){
if(!str2.contains(String.valueOf(c))){
System.out.println("Strings are Anagrams");
anagram = false;
}

if(anagram == true){
System.out.println("Strings are not Anagrams");
}
}
}

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   Like         Discuss         Correct / Improve      check if 2 strings are Anagrams     Asked in 30 Companies      basic        frequent

 Q284. Difference between new operator and Class.forName().newInstance() ?
Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.

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 Q285. Difference between ArrayList and LinkedList ?
Ans. LinkedList and ArrayList are two different implementations of the List interface. LinkedList implements it with a doubly-linked list. ArrayList implements it with a dynamically resizing array.

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 Q286. What are the pre-requisite for the collection to perform Binary Search ?
Ans. 1. Collection should have an index for random access.
2. Collection should have ordered elements.

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   Like         Discuss         Correct / Improve     java   collections   search algorithm   search   binary search   at&t      intermediate

 Q287. Which of the following syntax is correct ?import static java.lang.System.*;or static import java.lang.System.*;Core Java
Ans. import static java.lang.System.*;

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 Q288. What will be the output of following Code ?

class BuggyBread {
   public static void main(String[] args) {
      String s2 = "I am unique!";
      String s5 = "I am unique!";

      System.out.println(s2 == s5);
   }
}		Core Java
Ans. true, due to String Pool, both will point to a same String object.

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 Q289. What will be the output of following code ?
class BuggyBread2 {       
   private static int counter = 0;     
   void BuggyBread2() {        
      counter = 5;    
   }     
   
   BuggyBread2(int x){
      counter = x;    
   }        

   public static void main(String[] args) {        
      BuggyBread2 bg = new BuggyBread2();        
      System.out.println(counter);    
   } 
}		Core Java
Ans.  Compile time error as it won't find the constructor matching BuggyBread2(). 
Compiler won't provide default no argument constructor as programmer has already defined one constructor. 
Compiler will treat user defined BuggyBread2() as a method, as return type ( void ) has been specified for that. 

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 Q290. 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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