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Q1181. What is the difference between being final and being immutable ? Are string final or immutable in Java ?

Ans. Being final in the sense of objects or object reference means that the reference cannot be reassigned to a different object whereas being immutable means that the object contents cannot be changed.

Strings in Java are immutable.

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_{Like Discuss Correct / Improve string immutable immutability final vs immutable immutability}

Q1182. What does the following initialization mean ?

ArrayList<LinkedList> traversalPaths = new ArrayList<LinkedList>();

What could be the use of such a collection.

Ans. Initialize an ArrayList that will hold LinkedLists i.e every element of the arraylist will be a linked list.

Such collection could be used in algorithms that require first random access and then sequential traversal. For example - Storing traversal paths for a graph wherein we can start from any vertex. Implementing dictionary with each arraylist element holding staring with character and then linked list holding duplicate words.

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Q1183. What will be the output upon executing main method

public class Graph {
   private static Multimap<Integer,Integer> adjacentDirectedNodesMap = ArrayListMultimap.create();

   Graph(){
      adjacentDirectedNodesMap.put(1, 2);
      adjacentDirectedNodesMap.put(1, 3);
      adjacentDirectedNodesMap.put(1, 4);
      adjacentDirectedNodesMap.put(3, 5);
      adjacentDirectedNodesMap.put(4, 5);
   }

   public static void main(String[] args){
      ArrayList visited = new ArrayList();

      Integer startNode = 1;

      for(Integer adjacentNodes: adjacentDirectedNodesMap.get(startNode)){
            System.out.println(adjacentNodes);
      }
   }
}

Ans. Nothing as we haven't yet created an instance and hence adjacentDirectedNodesMap won't be initialized with any value and hence is empty.

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Q1184. What is the difference between return and continue statement ?

Ans. return is used within a method to return control out of the method. It may be followed by a value which is returned from the method to calling method immediately preceding the point of call.

continue statement is used within a loop to start next iteration without executing the remaining statements in the loop.

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_{Like Discuss Correct / Improve return statement continue statement return vs continue for loop control statements loop statement}

Q1185. What is the difference between return and break statement ?

Ans. return is used within a method to return control out of the method. It may be followed by a value which is returned from the method to calling method immediately preceding the point of call.

break statement is used within a loop to move control out of the loop.

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_{Like Discuss Correct / Improve return statement break statement return vs break}

Q1186. What is the difference between Java SE Map and Apache Commons MultiMap ? How can we implement functionality similar to multimap using Java SE map ?

Ans. We can have duplicate keys within MultiMap whereas we cannot have duplicate keys within Java Util Map.

We can have a Map with value as a "collection of values" instead of single value to have a similar function as Multimap.

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Q1187. What is the difference between hasNextInt and nextInt method of scanner class ?

Ans. The hasNextInt() is used to check if there are any more elements left and the nextInt() is used to access that element.

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Q1188. Is it a bad practice to initialize object reference to Null ?

Ans. never initialise local to null,yes it is bad pratice

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Q1189. What will be the output of following code and Why ?

int x = 5;
int y = 7;
float f = 5f;
float z = y / x * f;
System.out.println(z);

Ans. 5.0

operation between two ints generate int only. so 7/5 generates 1 and not 1.4. Multiplication between int and float generates float and hence

1 * 5.0 = 5.0

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_{Like Discuss Correct / Improve arithmetic calculation data types}

Q1190. How do you know if a method is a constructor ?

Ans. Is the method name same as class Name - Yes

Does the method have any return type ( even void ) - No

It's a constructor

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Q1191. Is a string an array of characters in Java ?

Ans. No, String is a class whose objects are called strings in Java.

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Q1192. Can we synchronize the run() method in Java?

^{This question is still unanswered. Can you please provide an answer.}

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Q1193. Difference between if and switch ? Can we replace all switch statements with if statements ?

Ans. if statement is used to do 2 direction branching whereas switch is used to do multi direction branching in Java.

Yes we can replace all switch statements with nested if statements.

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Q1194. What is nested if ?

Ans. if statements nested within another if or else blocks are called nested if statements.

if(condition1) {
if(condition2){
}
}

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Q1195. Write a Program to check if the entered number is a Duck Number ( Number having 0 in it ) ?

^{This question is still unanswered. Can you please provide an answer.}

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Q1196. What will the following code print ?

int x[] = new int[5];
x[0] = 1;
x[1] = 2;

for(int count=0;count<x.length;count++){
System.out.println(x[count]);
}

Ans. 1
2
0
0
0

As arrays are not dynamically expanded , we have declared the array for size 10. As we have only initialized only 2 values , it will print rest as their default values.

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Q1197. What will the following code print

int x[] = new int[5];
x[0] = 1;
x[1] = 2;

for(int count=0;count<=x.length;count++){
System.out.println(x[count]);
}

Ans. 1
2
0
0
0
ArrayIndexOutOfBoundException: 5

As array index starts with 0 and ends with the index of (size - 1), the index 5 is inaccessible for the array and hence will throw the exception.

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Q1198. what are different pointer operators used ?

^{This question was recently asked at 'Huawei Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q1199. What is mutable in Java ?

^{This question is still unanswered. Can you please provide an answer.}

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Q1200. Which java features makes java different from other languages ?

^{This question is still unanswered. Can you please provide an answer.}

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Q1201. Why cant we start an identifier with a number in Java?

^{This question is still unanswered. Can you please provide an answer.}

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Q1202. What is the default data type of Serialized methods?'

^{This question was recently asked at 'Intime Tec'.This question is still unanswered. Can you please provide an answer.}

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Q1203. Do we have a method to reverse a string in String class ?

Ans. No but we have it in StringBuilder.

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Q1204. How can we convert char into a String ?

Ans. We can use StringBuilder. StringBuilder accepts char as the argument for it's constructor.

new StringBuilder('').toString();

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Q1205. How can we check if a particular character is upper case in Java ?

Ans. 1. We can compare the ascii value of the character. Ascii for Capital case character is from 65 to 90.

2. We can compare to see if lowerCase of the character is not equal to character itself.

For example -

if character is 'a' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return true and hence char is lower case

if character is 'A' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return false and hence char is upper case

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_{Like Discuss Correct / Improve check upper case character character}

Q1206. How different is it when final applied to variables and object references ?

Ans. final when assigned to object references doesn't make them immutable. It means that the references cannot be de-referenced.

final when applied to variables means that the value cannot be changed.

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Q1207. Why the following code produced this output ?

int x = 5;
int y = x;
y = 10;

System.out.println(x); // prints 5 and not 10

Ans. Because when we say y = x, the value of x is copied to another memory location and then y points to that new memory location.

Unlike object references that once assigned point to same object in memory, value is copied in case of variable assignment.

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Q1208. In which memory segment - heap or stack, the following stored by JVM

1. static members
2. objects
3. object references
4. local or method variables

Ans. static members are stored in method area of heap

objects are stored on heap

object references are stored on stack

local or method variables are stored on stack

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_{Like Discuss Correct / Improve jvm memory management stack heap}

Q1209. How can we convert String into Char array and vice versa ?

Ans. There is a method toCharArray() within String class that can be used to convert string to char array.

string.toCharArray();

String class has an argument constructor that takes a char array and create a string

new String(charArray);

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Q1210. How can we convert a character or a character array into a String ?

Ans. String has an argument constructor that take char array as argument and creates a string.

There is no constructor available with String that takes in a character and creates a String. We can use StringBuilder which has a char argument constructor.

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