Rarely asked Interview Questions and Answers

Interview Questions and Answers - Order By Rating

Q31. Can I hit the Rest Post Request through a browser address bar if it's not expecting any payload / body ?

Ans. No, even if there is no payload, you can't hit the POST request by typing it into browser address bar. You will need a client that can make a POST Request.

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Q32. Is it Necessary to send a POST request with the Payload or a body ?

Web Service

Ans. No, we can also send an empty body with the POST Request.

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Q33. What is "Instance Initializer block" ?

Ans. Instance Initializer block is used to initialize the instance data member. It run each time when object of the class is created.

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Q34. What is servlet Chaining ?

Java EE

Ans. Multiple servlets serving the request in chain.

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Q35. What are the Wrapper classes available for primitive types ?

Core Java

Ans. boolean - java.lang.Boolean
byte - java.lang.Byte
char - java.lang.Character
double - java.lang.Double
float - java.lang.Float
int - java.lang.Integer
long - java.lang.Long
short - java.lang.Short
void - java.lang.Void

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Q36. What are concepts introduced with Java 5 ?

Core Java

Ans. Generics , Enums , Autoboxing , Annotations and Static Import.

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Q37. Does Constructor creates the object ?

Core Java

Ans. New operator in Java creates objects. Constructor is the later step in object creation. Constructor's job is to initialize the members after the object has reserved memory for itself.

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Q38. Which String class does not override the equals() and hashCode() methods, inheriting them directly from class Object?

Core Java

Ans. java.lang.StringBuffer.

Sample Code for StringBuffer

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Q39. Which interface does java.util.Hashtable implement?

Core Java

Ans. Java.util.Map

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Q40. Can we serialize static variables ?

Core Java

Ans. No. Only Object and its members are serialized. Static variables are shared variables and doesn't correspond to a specific object.

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Q41. Difference between long.Class and Long.TYPE ?

Ans. They both represent the long primitive type. They are exactly the same.

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Q42. What are the common uses of "this" keyword in java ?

Core Java

Ans. "this" keyword is a reference to the current object and can be used for following -

1. Passing itself to another method.

2. Referring to the instance variable when local variable has the same name.

3. Calling another constructor in constructor chaining.

Sample Code for this keyword

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Q43. Can constructors be synchronized in Java ?

Core Java

Ans. No. Java doesn't allow multi thread access to object constructors so synchronization is not even needed.

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Q44. What are transient variables in java?

Core Java

Ans. Transient variables are variable that cannot be serialized.

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Q45. What is the difference between time slicing and preemptive scheduling ?

Operating System

Ans. In preemptive scheduling, highest priority task continues execution till it enters a not running state or a higher priority task comes into existence. In time slicing, the task continues its execution for a predefined period of time and reenters the pool of ready tasks.

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Q46. Which memory segment loads the java code ?

Core Java

Ans. Code segment.

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Q47. Can a lock be acquired on a class ?

Ans. Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.

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Q48. Are constructors inherited? Can a subclass call the parent's class constructor? When?

Core Java

Ans. You cannot inherit a constructor. That is, you cannot create a instance of a subclass using a constructor of one of it's superclasses. One of the main reasons is because you probably don't want to override the superclasses constructor, which would be possible if they were inherited. By giving the developer the ability to override a superclasses constructor you would erode the encapsulation abilities of the language.

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Q49. What is the role of JSON.stringify ?

Json

Ans. JSON.stringify() turns an object into a JSON text and stores that JSON text in a string.

So If we stringfy above notation , it will become

{"name":"xyz","gender":"male";"age":30}

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Q50. What is URL?

Java EE

Ans. URL is Uniform Resource Locator which is representation of HTTP address.

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Q51. Can I import same package/class twice? Will the JVM load the package twice at runtime?

Core Java

Ans. One can import the same package or same class multiple times. Neither compiler nor JVM complains wil complain about it. And the JVM will internally load the class only once no matter how many times you import the same class.

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Q52. Difference between boolean and Boolean ?

Core Java

Ans. boolean is a primitive type whereas Boolean is a class.

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Q53. Will Compiler creates a default no argument constructor if we specify only multi argument constructor ?

Ans. No, Compiler will create default constructor only if we don't specify any constructor.

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Q54. Can we use both "this()" and "super()" in a constructor ?

Core Java

Ans. No, because both this and super should be the first statement.

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Q55. Can we declare an abstract method private ?

Ans. No Abstract methods can only be declared protected or public.

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Q56. What is suspend() method used for ?

Ans. suspend() method is used to suspend the execution of a thread for a period of time. We can then restart the thread by using resume() method.

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Q57. Difference between suspend() and stop() ?

Ans. Suspend method is used to suspend thread which can be restarted by using resume() method. stop() is used to stop the thread, it cannot be restarted again.

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Q58. Will this code give error if i try to add two heterogeneous elements in the arraylist. ? and Why ?

List list1 = new ArrayList<>();
list1.add(5);
list1.add("5");

Ans. If we don't declare the list to be of specific type, it treats it as list of objects.

int 1 is auto boxed to Integer and "1" is String and hence both are objects.

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Q59. What is the difference between System.console.write and System.out.println ?

Ans. System.console() returns null if your application is not run in a terminal (though you can handle this in your application)System.console() provides methods for reading password without echoing charactersSystem.out and System.err use the default platform encoding, while the Console class output methods use the console encoding

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Q60. Which load testing tools have you used ?

Ans. Rational Robot, JMeter, LoadRunner

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