SDE - 1

1) In object-oriented programming, a singleton class is a class that can have only one object (an instance of the
class) at a time.

2) After first time, if we try to instantiate the Singleton class, the new variable also points to the first instance created.

3) So whatever modifications we do to any variable inside the class through any instance, it affects the variable of the
single instance created and is visible if we access that variable through any variable of that class type defined.

The key points while defining class as singleton class are :

1) Make constructor private.
2) Write a static method that has return type object of this singleton class. Here, the concept of Lazy initialization is
used to write this static method.

Answer :
1) Garbage Collection in Java is a process by which the programs perform memory management automatically.

2) The Garbage Collector(GC) finds the unused objects and deletes them to reclaim the memory.

3) In Java, dynamic memory allocation of objects is achieved using the new operator that uses some memory and the
memory remains allocated until there are references for the use of the object.

4) When there are no references to an object, it is assumed to be no longer needed, and the memory, occupied by
the object can be reclaimed.

5) There is no explicit need to destroy an object as Java handles the de-allocation automatically.

The technique that accomplishes this is known as Garbage Collection. Programs that do not de-allocate memory can
eventually crash when there is no memory left in the system to allocate. These programs are said to have memory
leaks.

Garbage collection in Java happens automatically during the lifetime of the program, eliminating the need to de-
allocate memory and thereby avoiding memory leaks.
In C language, it is the programmer’s responsibility to de-allocate memory allocated dynamically using free() function.

This is where Java memory management leads.

Solved by using simple two pointer approach

NORMALIZATION :
1) Normalization is a process of reducing redundancy by organizing the data into multiple tables.
2) Normalization leads to better usage of disk spaces and makes it easier to maintain the integrity of the database.


DENORMALIZATION :
1) Denormalization is the reverse process of normalization as it combines the tables which have been normalized into
a single table so that data retrieval becomes faster.
2) JOIN operation allows us to create a denormalized form of the data by reversing the normalization.

Constructors :
1) A Constructor is a block of code that initializes a newly created object.
2) A Constructor can be used to initialize an object.
3) A Constructor is invoked implicitly by the system
4) A Constructor is invoked when a object is created using the keyword new.
5) A Constructor doesn’t have a return type.
6) A Constructor’s name must be same as the name of the class.
7) A Constructor cannot be inherited by subclasses.


Method :
1) A Method is a collection of statements which returns a value upon its execution.
2) A Method consists of Java/C++ code to be executed.
3) A Method is invoked by the programmer.
4) A Method is invoked through method calls.
5) A Method must have a return type.
6) A Method’s name can be anything.
7) A Method can be inherited by subclasses.

Steps :
Let's call 5L jar as X and 3L jar as Y.
1) We'll take the first jar, i.e, X. Fill X completely.
2) Then empty the X content in Y. We are left with 2 L in the X.
3) Now we will empty the Y jar and then Fill 2L from X into Y. We are left with 0L in X and 2L in Y.
4) Now again we will fill X with 5L and then empty till Y gets full.
5) As Y is already full with 2L from previous operation so it can only accomodate 1L now from X. So when
Y jar is full automatically we will have 4L left in X. This is how we will calculate 4L