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Ans. What if the initialization throws an exception. In that case , it will let it move forward without initializing the final field. So it's a way to enforce that either the field is initialized or it fails completely.
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Ans. Session storage can be accessed from XSS (Cross site Scripting) attacks but cookies (if set with "HttpOnly" and "Secure" flags) are more safer against these attacks.
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Ans. Inheritance is one of the key principle of object oriented programming. Through inheritance, one class can inherit the properties of another class. The class from which properties are inherited is called super class and the class to which properties are inherited is called sub class.
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Ans. Static method is common to all instances of a class. Static methods are stored in the class memory. Whereas non-static methods are stored in the object memory. Each instance of a class will have their own copy of non-static methods.
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Ans. Looping is used in programming to execute a statement or a block of statement repeatedly. There are three types of loops in Java:
1) For Loops
For loops are used in java to execute statements repeatedly for a given number of times. For loops are used when number of times to execute the statements is known to programmer.
2) While Loops
While loop is used when certain statements need to be executed repeatedly until a condition is fulfilled. In while loops, condition is checked first before execution of statements.
3) Do While Loops
Do While Loop is same as While loop with only difference that condition is checked after execution of block of statements. Hence in case of do while loop, statements are executed at least once.
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Ans. In java, float takes 4 bytes in memory while Double takes 8 bytes in memory. Float is single precision floating point decimal number while Double is double precision decimal number.
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Ans. An array groups data of same primitive type and is static in nature while vectors are dynamic in nature and can hold data of different data types.
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Ans. These frameworks facilitates easier product development and enhancement and maintainability by having separation of concerns ( using oops ) and helps in development of reusable libraries / components. So in nutshell , they make development and maintenance of large scale application easier.
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Ans. Session Cookie, because session storage can be accessed from XSS (Cross site Scripting) attacks but cookies (if set with "HttpOnly" and "Secure" flags) are more safer against these attacks.
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Ans. ConcurrentMap is an interface and it is a member of the Java Collections Framework. It represents a Map that is capable of handling concurrent access to it without affecting the consistency of entries in a map. ConcurrentMap interface present in java.util.concurrent package.
HashMap operations are not synchronized, while Hashtable provides synchronization. Though Hashtable is thread-safe, it is not very efficient. To solve this issue, the Java Collections Framework introduced ConcurrentMap in Java 1.5.
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Ans. 1. JVM that makes it platform independent and facilitates portability.
2. Garbage Collector that protects from Memory Leaks.
3. Only usage of references and not pointer arithmetic and hence protects the application from memory issues like dangling pointers, memory leaks etc.
4. Support for OOPs that makes application development and maintenance easy.
5. Facilitates library development through use of interface / abstract classes.
6. Facilitates creation of scalable applications.
7. Huge repository of libraries and pool of people with java skill.
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Ans. data under collection are actually stored in memory so that they can be retrieved when needed whereas data in streams are not stored and hence we need to construct it again when needed.
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