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Q31. What are benefits of strongly typing variables ?

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Q32. Difference between Let and Var in Javascript ?

Ans. Var scopes the variable to the nearest function whereas Let scopes the variable to nearest block.

For example -

function printNumbers() {
for(var i = 1; i < 3: i++){
console.log(i);
}

console.log(i); // works fine and will print 3 as i has a function scope and not local loop scope
}

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Q33. How can we create an arraylist of unique values ?

Ans. We can put the value in a set to enforce uniqueness and then dum those value into an arraylist.

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Q34. Why wait(), notify(), notifyAll() methods are in Object class instead of Thread class?

Ans. wait() and notify() methods are defined in Object class rather than Thread class.If wait() and notify() were on the Thread instead then each thread would have to know the status of every other thread and there is no way to know thread1 that thread2 was waiting for any resource to access.Hence, notify, wait, notifyAll methods are defined in object class in Java.

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Q35. Can the value of a static variable be changed ?

Ans. Yes the value of a static variable can be changed. It's the final keyword that restrict the modification of value not static.

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Q36. What are the advantages and disadvantages of Lambda Expression ?

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Q37. Write a unit test case using java 8.

Ans. public List convertAllToUpperCase(List words) {
return words.stream().map(String::toUpperCase).collect(Collectors.toList());
}

@Test
public void testAllToUpperCase() {
List expected = Arrays.asList("JAVA8", "STREAMS");
List result = convertAllToUpperCase(Arrays.asList("java8", "streams"));
assertEquals(expected, result);
}

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Q38. Write a program to make an array act as a set.

Ans. public Set convertArrayToList(T array[]) {
Set set = new HashSet<>(Arrays.asList(array));
return set;
}

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Q39. What is the use of defining equals , compareTo and hashcode methods in a class ? Where are they used ?

Ans. equals, compareTo and hashcode are of use when the objects are used within collections.

Equals helps with collections that helps maintaining only unique objects ( like Set )

compare and compareTo helps with collections that helps maintaining objects in order ( TreeSet, TreeMap etc )

hascode helps with collections that facilitates hash searching ( like hashSet, hashMap etc )

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Q40. prototypal inheritance in Javascript

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Q41. Have you had to work with memory leak problems in javascript ?

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Q42. Write a method to track every click on a page.

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Q43. What is the difference between inheritance in PHP vs. Javascript?

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Q44. Write a Program to draw a fish ?

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Q45. Should we do anything to avoid memory leaks in Java ?

Ans. Java has a intrinsic way of checking leaks and reclaiming memory called garbage collection. Moreover Java doesn't support pointer arithmetics , so there is very low comparative chance of memory leaks, compared to C,C++

Though there may be tools that may audit code to make sure that we are not leaving much for the garbage collection to work but I have never heard anyone doing anything for memory leaks in Java.

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Q46. Explain Collections in Java

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Q47. Is String mutable or immutable in Java ?

Ans. String is Immutable because of String Constant Pool.

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Q48. What are different types of Polymorphism in Java ?

Ans. run time polymorphism
compile time polymorphism

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Q49. Can we assign the reference to this variable ?

Ans. No

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Q50. Hash map using/without using Java 8

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Q51. What is Throwable ?

Ans. Throwable in java is a class that is the superclass of all exceptions and errors which may occurs in java program.It extends obcect class.

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Q52. What is Defer Parsing JavaScript ?

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Q53. What is string pool and what is the use of intern() function ?

Ans. The Java String class intern() method returns the interned string. It returns the canonical representation of string.

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Q54. How to make a collection thread safe?

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Q55. What is a comparator ?

Ans. Java Comparator compares two Java objects in a “compare(Object 01, Object 02)” format. Using configurable methods, Java Comparator can compare objects to return an integer based on a positive, equal or negative comparison

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Q56. Why should we go for custom defined exceptions even if we have many exceptions provided already using throw keyword

Ans. It gives us the liberty to throw the specific exceptions which are required and also we can control the handling of exceptions

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Q57. How does Garbage Collector work? What are the realizations of Garbage Collector.

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Q58. How multiple catch block works ?

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Q59. What is the use of toString method ?

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Q60. Class and Object methods.

Ans. class:- A class describe the contents of an object, an it describe the detail of data field called instance variable and defines the operations called method.

Object:-An object is an element of a class. Object have the behaviors of their class.

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