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

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Q1061. Create an event class in Java.

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Q1062. How does multi threading improve performance ?

Core Java

Ans. Every process in it's timeline require different resources. Utilization of resources can be optimized when they are shared among different processes or threads. When one thread is sleeping waiting for a peripheral to complete (e.g. a disk write, or a key press from the keyboard), other threads can continue using processor time and hence would lead to better usage of resources.

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Q1063. What are the different ways to avoid multi Threading related problems in Java ?

Core Java

Ans. Synchronization,
Concurrent classes,
Volatile keyword,
Implementing concurrent Lock interface,
Immutable classes

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Q1064. What is context switching wrt Threads in Java?

Core Java

Ans. Context Switching is the process of storing and restoring of CPU state so that Thread execution can be resumed from the same point at a later point of time.

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Q1065. What is Lock interface in Java Concurrency API ?

Core Java

Ans. Lock interface provide more extensive locking. They allow more flexible structuring and may support multiple associated Condition objects.

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Q1066. Why Concurrent Collection Classes are fail-fast in Java ?

Core Java

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Q1067. Can a class extend itself in Java ?

Core Java

Ans. No

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Q1068. What is method hiding in Java ?

Core Java

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Q1069. Can you prevent overriding a method without using final modifier or without declaring it private ?

Core Java

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Q1070. Can we override a non-static method as static in Java ?

Core Java

Ans. No, there is no method overriding with static methods.

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Q1071. Can we declare constructor inside an interface ? Why ?

Core Java

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Q1072. Can we declare an Interface with abstract keyword ?

Core Java

Ans. Yes

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Q1073. Does Java generate .class file for interfaces ?

Core Java

Ans. Yes

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Q1074. How arrays work internally ?

Core Java

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Q1075. Can we change the size of array once created ?

Core Java

Ans. No. Arrays cannot resize dynamically.

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Q1076. Can we use generics with arrays in Java ?

Core Java

Ans. No

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Q1077. What is the difference between ArrayIndexOutOfBoundException and ArrayStoreException?

Core Java

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Q1078. What is ArrayStoreException ?

Core Java

Ans. It's an exception that is thrown when we attempt to add value of an incompatible type to an array.

For example -

Object[] strArray = new String[2];
strArray[0] = 5;

In this code, strArray reference of type Object has currently been assigned the String array but at line 2 we are trying to add an integer value.

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Q1079. What is an anonymous array in Java ?

Core Java

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Q1080. What are jagged arrays ?

Core Java

Ans. an array of different sizes

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Q1081. Where are arrays stored in memory - stack or heap ?

Core Java

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Q1082. Are Arrays treated like primitives or like objects in Java ?

Core Java

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Q1083. How can we check equality for Arrays in Java ?

Core Java

Ans. You call the method java.util.Arrays.equals(Object[] a, Object[] a2)?

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Q1084. Are arrays Thread Safe ?

Core Java

Ans. Yes

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Q1085. What is the time and space complexity for different operations for arrays ?

Core Java

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Q1086. Write code to serialize and deserialize an array of strings ?

Core Java

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Q1087. Can we have 3 dimensional arrays in Java ?

Core Java

Ans. Yes

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Q1088. Can we make array volatile in Java ?

Core Java

Ans. Yes, you can make an array (both primitive and reference type array e.g. an int array and String array) volatile in Java but only changes to reference pointing to an array will be visible to all threads, not the whole array

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Q1089. How do you implement 'state and behavior' of object in Java program?

Core Java

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Q1090. How is it possible to use concat on string objects in Java, based on the fact that string is immutable?

Core Java

Ans. It's possible because internally java first reserves the memory for the new concatenated string and then copy that over. So after concatenation, there are 2 strings in memory, the original one and the concatenated one and then the reference is moved to the concatenated string.

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