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Ans. Java was initially found in 1991 by James Gosling, Sun Micro Systems. At first it was called as "Oak". In 1995 then it was later renamed to "Java". java is a originally a platform independent language. Currently Oracle, America owns Java.
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Ans. It is used to sort collections and arrays of objects using the collections.sort() and java.utils. The objects of the class implementing the Comparable interface can be ordered.
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Ans. Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism.
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Ans. Since String is immutable, its hashcode is cached at the time of creation and it doesnt need to be calculated again. This makes it a great candidate for key in a Map and its processing is fast than other HashMap key objects. This is why String is mostly used Object as HashMap keys.
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Ans. substring method would build a new String object keeping a reference to the whole char array, to avoid copying it. Hence you can inadvertently keep a reference to a very big character array with just a one character string.
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Q347. Difference between new operator and Class.forName().newInstance() ?
Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.
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Q348. Difference between ArrayList and LinkedList ?
Ans. LinkedList and ArrayList are two different implementations of the List interface. LinkedList implements it with a doubly-linked list. ArrayList implements it with a dynamically resizing array.
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Ans. Compile time error as it won't find the constructor matching BuggyBread2().
Compiler won't provide default no argument constructor as programmer has already defined one constructor.
Compiler will treat user defined BuggyBread2() as a method, as return type ( void ) has been specified for that.
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Constructor provided by Java if no constructor is declared
Constructor with empty body
All of the above
How can we create objects if we make the constructor private ?
We can't create objects if constructor is private
We can only create objects if we follow singleton pattern
We can only create one object
We can create new object through static method or static block
What is the problem with following code ?
public class Car extends Vehicle{
int x;
void Car(int y){
x = 5;
}
void Car(){
this(5);
}
}
We cannot use this() within normal method
We cannot chain methods
We cannot overload constructors
We cannot use return type void with overloaded methods
Q353. What are temp tables ?
Ans. These are the tables that are created temporarily and are deleted once the Stored Procedure is complete.
For example - we may like to pull some info from a table and then do some operations on that data and then store the output in final output table. We can store the intermediary values in a temp table and once we have final output with us, we can just delete it.
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