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Q1281. Write a Program to find number of lines , words and characters in a File.

Ans. import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileUtility {

public static void main(String[] args) {
System.out.println(printFile("/home/userme/notes"));
}

private static int printFile(String filePath) {
int wordCount = 0;
try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
String line = null;
String[] wordsArray = null;

while ((line = br.readLine()) != null) {
wordsArray = line.split(" ");
wordCount = wordsArray.length;
}
} catch (IOException e) {
e.printStackTrace();
}
return wordCount;

}
}

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Q1282. Given a String with some Code, Write a Parser to have proper indentation.

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Q1283. How do you make instance of an abstract class ?

Ans. By extending it to the derived class and thereby creating instance of derived class.

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Q1284. Explain how Mark & Sweep is implemented in garbage collection.

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Q1285. How would you stop a Thread in java ?

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Q1286. Write code for serialization.

Ans. // Java code for serialization and deserialization
// of a Java object
import java.io.*;

class Demo implements java.io.Serializable
{
   public int a;
   public String b;

   // Default constructor
   public Demo(int a, String b)
   {
      this.a = a;
      this.b = b;
   }

}

class Test
{
   public static void main(String[] args)
   {
      Demo object = new Demo(1, "geeksforgeeks");
      String filename = "file.ser";

      // Serialization
      try
      {
         //Saving of object in a file
         FileOutputStream file = new FileOutputStream(filename);
         ObjectOutputStream out = new ObjectOutputStream(file);

         // Method for serialization of object
         out.writeObject(object);

         out.close();
         file.close();

         System.out.println("Object has been serialized");

      }

      catch(IOException ex)
      {
         System.out.println("IOException is caught");
      }

      Demo object1 = null;

      // Deserialization
      try
      {
         // Reading the object from a file
         FileInputStream file = new FileInputStream(filename);
         ObjectInputStream in = new ObjectInputStream(file);

         // Method for deserialization of object
         object1 = (Demo)in.readObject();

         in.close();
         file.close();

         System.out.println("Object has been deserialized ");
         System.out.println("a = " object1.a);
         System.out.println("b = " object1.b);
      }

      catch(IOException ex)
      {
         System.out.println("IOException is caught");
      }

      catch(ClassNotFoundException ex)
      {
         System.out.println("ClassNotFoundException is caught");
      }

   }
}

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Q1287. If compareTo() method returns zero, does it mean that the objects are always equal?

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Q1288. Write a method receiving a stream of integers, caching the last 10 min of data and returning a number if it's less than the current input

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Q1289. How would you write a socket in Java

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Q1290. Why do you think lambda expressions are considered such a big thing for Java 8?

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Q1291. What are the drawbacks of creating immutable objects ? Why don't we create all object immutable if mutability possesses so much threat ?

Ans. Immutable objects relieves us from the problems of inconsistencies and security and helps with better read performance but at the same time are write performance and storage overheads. In case any modification is required , a new object is created and thus creating multiple copies of it.

This is the reason we use StringBuffer / StringBuilder when we have to append some text multiple times and then create a String out of it.

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Q1292. Does immutability facilitates better performance ?

Ans. Yes , but only the read performance in case we don't need to modify it much. In case we need to modify it a lot , it creates write performance overheads as we would need to create many news objects instead of just changing one.

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Q1293. Do you think that Recursion is expensive on computation ?

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Q1294. Write a program to rotate array elements clockwise.

Ans. class Rotate{

void leftRotate(int arr[], int d, int n)
{
for (int i = 0; i < d; i )
leftRotatebyOne(arr, n);
}

void leftRotatebyOne(int arr[], int n)
{
int i, temp;
temp = arr[0];
for (i = 0; i < n - 1; i )
arr[i] = arr[i 1];
arr[i] = temp;
}

void printArray(int arr[], int n)
{
for (int i = 0; i < n; i )
System.out.print(arr[i] " ");
}

public static void main(String[] args)
{
Rotate rotate = new Rotate();
int arr[] = { 1, 2, 3, 4, 5, 6, 7 };
rotate.leftRotate(arr, 2, 7);
rotate.printArray(arr, 7);
}
}

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Q1295. Given an array with number 1 to n, find the missing numbers.

Ans. int main ()
{
int a []={1..n};
int miss=getMiss (a,n);
Printf ("%d",miss);
}
getMiss (int a [],int n){
int I,total;
total=(n 1)*(n 2);
for (i = 0; i < n; i++)
total -= a[i];
return total;
}

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Q1296. Write a program to find the 10th prime number.

Ans. import java.util.Scanner;
public class Prime
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("Enter n to compute the nth prime number: ");
int nth = sc.nextInt();
int num, count, i;
num=1;
count=0;

while (count < nth){
num=num 1;
for (i = 2; i <= num; i )
{
if (num % i == 0)
{
break;
}
}
if ( i == num)
{
count = count 1;
}
}
System.out.println("Value of nth prime: " num);
}
}

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Q1297. Write a program to find length of String without using library function.

Ans. Class lengofstring {
Public static void main(String[] arr) {
int i = 0;
String s = "hello world!";
for (char C: s.toCharArray()) i;
System.out.println("Length: "
i);
}
}

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Q1298. Write a custom exception.

Ans. if you are creating your own exception is known as custom exception.

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Q1299. What is an exception ? What are the different types of exceptions ?

Ans. An exception is an unwanted or unexpected event, which occurs during the execution of a program that is at run time, that disrupts the normal flow of the program?s instructions. these are different types arithmetic exceptions, class not found exception, interrupted exception, run time exception etc.

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Q1300. Why use Java ?

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Q1301. Is HttpServlet an abstract class ?

Ans. Yes

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Q1302. Why do we need ConcurrentHashMap ?

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Q1303. What is the default size of ArrayList ?

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Q1304. Find minimum operations required to convert one string to another. Allowed operation :Insertion Deletion Replace, all operational costs are same.

Ans. StringBuilder str = new StringBuilder("Pizza");
int size = str.length();
str = str.replace(size-1, size, "u");
System.out.println("After replace, str = " str); // prints Pizzu

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Q1305. Write code to read data from a file and write it to a file with 2 threads using the thread name content

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Q1306. What is the need for filters in Java Servlets ?

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Q1307. What is the difference between Interfaces and Abstract Classes with respect to Java 8 ?

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Q1308. Which of the OOP's feature - encapsulation or abstraction - is more important ?

Ans. Encapsulation facilitates security by hiding data and logic whereas Abstraction simplifies organization of data and related logic.

As applications scale, both concepts are required for easy management and maintenance. Encapsulation for security and criss cross communication between objects / modules will make it vulnerable. and Abstraction for better organization that enables better understanding of application code and easy maintainability.

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Q1309. Which of the polymorphism type - static or runtime - is more important ?

Ans. Method overloading / static polymorphism compared to method overriding / runtime polymorphism has very limited usage as it just opens up an alternate way of defining a different method with the same name.

Method Overriding on other hand opens up many other features like contracting , interfacing , pluging development and hence development of libraries and frameworks.

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Q1310. What is the reason that non-static method are not allowed to be referenced from a static context in Java?

Ans. If we try to access an instance method from a static context , the compiler has no way to guess which instance method ( variable for which object ), you are referring to. Though, you can always access it using an object reference.

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