Core Java - Interview Questions and Answers for 'Core Java' | Search Interview Question

Interview Questions and Answers - Order By Rating

Q61. Is it possible to have a static class ?

Core Java

Ans. We can have a static inner class but not static outer class.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q62. Difference between List and LinkedList ?

Core Java

Ans. A List is an child interface of collection interface in java where as Linked list is and implementation class of List interface which has doubly linked as a underlying data structure

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve linkedlist list vs linkedlist Asked in 1 Companies}

Q63. Why packages are used in Java ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q64. What is meant by platform ? Which platform does java provides ?

Core Java

Ans. platform is the hardware or software environment in which a program runs. There are two types of platforms software-based and hardware-based. Java provides software-based platform.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q65. Write an algorithm for square root of a given number.

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q66. Which is faster, LinkedList or ArrayList?

Core Java

Ans. ArrayList is fast for random access, but is slow on deletion and insertion.

LinkedList is slow for random access, but is fast on deletion and insertion.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q67. Difference between function overloading and method overloading?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q68. Which interface is used for hashset implementation ?

Core Java

Ans. HashSet implements Set interface.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q69. why string pool concept for only String but not for StringBuffer ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q70. why string pool concept for only String but not for StringBuffer ?

Core Java

Ans. As String is immutable so by maintaining pool area we can refer the object to same area if they are with same content. But when it comes to string buffer or builder then due to mutable property if we do so then all the objects referring to that area will from now has new content.. So as to avoid this pool is present only in string.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q71. Can you give me a use case where you utilized serialization in your project code?

Core Java

Ans. we use serialization when we send response to client in JSON format.(the process of converting model object into json is nothing but serialization

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve serialization Asked in 1 Companies}

Q72. Write program to recursively iterate through map ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q73. Difference between interface and inheritance

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q74. Combine and join integer and string list to single list and sort.

Core Java

Ans. Object[] combined = new Object[first.length second.length];
System.arraycopy(first, 0, combined, 0, first.length);
System.arraycopy(second, 0, combined, first.length, second.length);

-- OR --

Object[] combined = Stream.concat(Arrays.stream(first), Arrays.stream(second)).toArray();

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q75. What are the 22 possible values of x where x== -x (true) ?

Core Java

Ans. byte x = 0;
short x = 0;
char x = 0;
int x = 0;
int x = Integer.MIN_VALUE;
float x = 0.0f;
float x = -0.0f;
long x = 0;
long x = Long.MIN_VALUE;
double x = 0.0;
double x = -0.0;
Byte x = 0;
Short x = 0;
Character x = 0;
Integer x = 0;
Integer x = Integer.MIN_VALUE;
Float x = 0.0f;
Float x = -0.0f;
Long x = 0L;
Long x = Long.MIN_VALUE;
Double x = 0.0;
Double x = -0.0;

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q76. Can we increase the buffer size while working with Buffered Streams ? How ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q77. Can we disable auto flushing for PrintWriter ?

Core Java

Ans. Yes

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q78. Have you ever faced any problem because of PrintWriter buffer and autoflush mechanism ? How did you got rid of it ?

Core Java

Ans. Yes , we faced trouble once wherein we were trying to set certain elements to the PrintWriter. As in some cases the PrintWriter held too much information and hence it would get flushed before we could append those elements.

We disabled auto flushing and provided our own explicit flushing.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q79. What are meta classes in Java ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q80. What is something faulty about java ?

Core Java

Ans. Not purely object oriented Language.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve expert}

Q81. Can we have more than two constructors in a class ?

Core Java

Ans. Yes, through constructor overloading

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve constructor overloading}

Q82. If we have a return statement inside the finally block, Then what will happen ?

Core Java

Ans. Returning from inside a finally block will cause exceptions to be lost. A return statement inside a finally block will cause any exception that might be thrown in the try block to be discarded.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve exception handling finally block Asked in 1 Companies}

Q83. how hashmap work? Write a program that uses map interface ?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q84. Can we have two interfaces having method with same name and arguments?

Core Java

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q85. Can we load environment variables into Properties in Java ? How ?

Core Java

Ans. Yes

new Properties().putAll(System.getenv());

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java.util.properties environment variables}

Q86. Difference between System.getEnv and System.getProperties ?

Core Java

Ans. System.getEnv gets the environment variables where System.getProperties gets Java properties.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve System.getEnv System.getProperties environment variables}

Q87. Difference between HashMap and Dictionary in Java ?

Core Java

Ans. HashMap implements the Map interface while the Dictionary does not.

HashMap was introduced after HashTable and Dictionary.

Dictionary is currently obsolete in java.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve hashmap dictionary class}

Q88. Difference between TreeMap and SortedMap ?

Core Java

Ans. sortedMap is an interface ,while TreeMap is an implementation of sortMap.

We can not create an instance of sortedMap but we can create an instance of treeMap

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve treemap sortedmap}

Q89. Difference between ArrayList and HashSet ?

Core Java

Ans. ArrayList is a list , i.e an implementation of List interface whereas HashSet is a Set and an implementation of Set interface.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arraylist hashset}

Q90. difference between ArrayList and array ?

Core Java

Ans. ArrayList is a variable length collection class whereas arrays are fixed length primitive structure.

We can use generics with arraylist but not with arrays.

We can store primitive data types within arrays but can't with ArrayList. In ArrayList that needs to be converted to Wrapper objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arraylist arrays collection classes collections basic frequent}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.