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

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Q1021. How do we do Inheritance in Java ?

Core Java

Ans. By extending class or implementing interface.

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Q1022. Difference between 32 bit and 64 bit JVM ?

Core Java

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Q1023. Tell about shallow and deep cloning ?

Core Java

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Q1024. Difference between final and finally

Core Java

Ans. final can be used for variables , methods and class. A final variable cannot be changed , a final method cannot be overridden , a final class cannot be inherited.

Finally is a block which is used after Try and catch, a finally block is always executed.

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Q1025. What will happen if there is an exception in Java finally block ?

Core Java

Ans. The regular behavior of exception handling will occur. It will look for any immediate catch handler and if none is provided, it would be transmitted to the callers until a catch handler is found or it's out of main function.

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Q1026. What is the default execution method in Java?

Core Java

Ans. public static void main(String[] args)

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Q1027. Can methods without a return type be declared in Java? Is there a difference between void return type and no return type ?

Core Java

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Q1028. how is the internal code for the "volatile" implemented ?

Core Java

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Q1029. Write Java code that would cause deadlock ?

Core Java

Ans. https://howtodoinjava.com/java/multi-threading/writing-a-deadlock-and-resolving-in-java/

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Q1030. is Java top down programming language or bottom up programming language?

Core Java

Ans. bottom up programming language

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Q1031. Can you name few Java packages which you frequently used ?

Core Java

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Q1032. How does encoding affect using Reader / writer classes or Stream classes in Java ?

Core Java

Ans. Which group of bytes represent which character is defined by character encoding. So when reading character by character from a stream of bytes using Reader, specifying character encoding becomes significant as the same group of bytes can represent different character in different character encoding(Eg UTF-8 and UTF-16 etc.)

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Q1033. How executor service is better than using primitive Threading mechanism using Thread class or runnable Interface ?

Core Java

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Q1034. What is the difference between TreeSet and TreeMap ?

Core Java

Ans. TreeSet contains only values as elements whereas TreeMap contains Key value pairs.

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Q1035. Which of the following is insertion heavy - HashSet or TreeSet ?

Core Java

Ans. TreeSet as it needs elements in a particular order

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Q1036. Write a Program to print a pattern ?

Core Java

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Q1037. Have you used Java 8 Lambda expressions ?

Core Java

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Q1038. How to calculate string length without using inbuilt function

Core Java

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Q1039. What is the difference between abstraction and abstract class ?

Core Java

Ans. Abstract class is one of the facility for achieving abstraction in Java.

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Q1040. Write code to print a Pyramid pattern ?

Core Java

Ans. public static void printTriagle(int n)
{
// outer loop to handle number of rows
// n in this case
for (int i=0; i1; j--)
{
// printing spaces
System.out.print(" ");
}

// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j=0; j<=i; j )
{
// printing stars
System.out.print("* ");
}

// ending line after each row
System.out.println();
}
}

// Driver Function
public static void main(String args[])
{
int n = 5;
printTriagle(n);
}

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Q1041. What does System.exit() do ?

Core Java

Ans. Generally used to indicate termination

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Q1042. How to sort objects based on one of the field ?

Core Java

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

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Q1043. Can we have interface as a replacement for utility class ?

Core Java

Ans. Yes, With Java 8 we can use Interfaces as collection of utility methods through the use of default methods.

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Q1044. What are custom annotations and How can we create one ?

Core Java

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Q1045. What is the difference between scope and access modifiers ?

Core Java

Ans. Scope modifiers changes the scope of a particular element or a method. For ex - static changes the scope of that of class and not of object.

Access modifiers changes the access priviledges of a particular element or a method. For ex - private , public etc.

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Q1046. Why Java has final class ?

Core Java

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Q1047. Which memory segment is cleaned by Garbage Collection - stack or heap ?

Core Java

Ans. Heap as objects are stored ink heap.

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Q1048. Do we have references for the objects that are eligible for garbage collection ?

Core Java

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Q1049. Are final methods faster than regular instance methods ?

Core Java

Ans. Yes. As they cannot be overridden , there is no use of virtual table concept which is used for dynamic binding resolution.

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Q1050. What is virtual table with respect to method overriding in Java ?

Core Java

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