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Q:

What is the difference between an Interface and an Abstract class? 

Answer:
Q:

What is the difference between creating String as new() and literal ?

Answer

When we create string with new() Operator, it’s created in heap and not added into string pool while String created using literal are created in String pool itself which exists in PermGen area of heap.



String s = new String("Test");

does not put the object in String pool , we need to call String.intern() method which is used to put them into String pool explicitly. its only when you create String object as String literal e.g. String s = "Test" Java automatically put that into String pool.

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1 29
Q:

What is immutable object? Can you write immutable object ?

Answer

Immutable classes are Java classes whose objects can not be modified once created. Any modification in Immutable object result in new object. For example is String is immutable in Java. Mostly Immutable are also final in Java, in order to prevent sub class from overriding methods in Java which can compromise Immutability. You can achieve same functionality by making member as non final but private and not modifying them except in constructor.

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2 51
Q:

Which two method you need to implement for key Object in HashMap ?

Answer

In order to use any object as Key in HashMap, it must implements equals and hashcode method in Java.

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2 42
Q:

How can you make sure your dependencies are safe ?

Answer

When writing Node.js applications, ending up with hundreds or even thousands of dependencies can easily happen.
For example, if you depend on Express, you depend on 27 other modules directly, and of course on those dependencies' as well, so manually checking all of them is not an option!


The only option is to automate the update / security audit of your dependencies. For that there are free and paid options:


1. npm outdated
2. Trace by RisingStack
3. NSP
4. GreenKeeper
5. Snyk

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1 56
Q:

What is the difference between ViewState and SessionState?

Answer

'ViewState' is specific to a page in a session.
'SessionState' is specific to user specific data that can be accessed across all pages in the web application.

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Subject: Java - Technology
Job Role: Analyst , IT Trainer

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