Java Programming
                     What is Java programming? 
Java: 
Java is a programming language and computing platform launched by Sun 
Microsystems in 1995. There are many applications and websites that will not 
work unless you have Java installed and they are created every day. Java is fast, 
safe and reliable. 
How does the java program work?
Compilation: In Java, programs are not compiled into executable files; they are
compiled in bytecode (as discussed above), which JVM (Java Virtual Machine) 
runs at run time. When the program is executed, the bytecode is converted using
the just-in-time compiler (JIT). 
Java uses a garbage collector to manage the memory in the life cycle of the 
object. The programmer determines when the objects are created and the Java 
Runtime is responsible for recovering the memory as soon as the objects are no 
longer in use. 
Java Runtime Environment (JRE), which contains the Java SE platform parts 
required to run Java programs and it is intended for end users. Allows you to 
declare a local variable without specifying its type. 
The type of variable is derived from the type of real object created. It is said to 
be the only real resource for developers in JDKOOP in Java.
The concepts of OOP in Java are the main ideas behind Java object-oriented 
programming. They are an abstraction, encapsulation, inheritance and 
polymorphism. 
Most people who are dedicated to the teaching of mathematics and mathematics
in the field of teaching. The idea of grouping data and methods that work on this
data in a unit is described, for example, a class in Java. This concept is also 
often used to hide the internal representation or state of an object on the outside.
In JDK, the components that made up a collector (GC) implementation were 
distributed by several parts of the code base. It has been changed in Java 10. 
Now, it is a clean interface in the JVM source code to allow the alternative 
collectors to be integrated quickly and easily. The isolation of the source code 
of different garbage collectors will be improved.
1)Abstraction: 
Abstraction (from the Latin abs, which means distancing and trahere, which 
means drawing) is the process of removing or eliminating characteristics of 
something to reduce it to a set of essential characteristics.
2)Encapsulation: 
Encapsulation in Java is a mechanism of wrapping the data (variables) and code
acting on the data (methods) together as a single unit. Declare the variables of a 
class as private.
3) inheritance: 
The inheritance can be defined as the process by which an object of one class 
acquires characteristics of the object of the other class. All objects of a similar 
type are grouped to form a class. 
4) Polymorphism: 
Generally, the ability to appear in many forms. In object-oriented programming,
polymorphism refers to the ability of a programming language to process 
objects differently, depending on their type or class of data. More specifically, it
is the ability to redefine methods for derived classes.
Javac in Java: 
 Javac is the primary Java compiler included in the Oracle Corporation's 
JavaDevelopment Kit (JDK). The compiler accepts the source code 
according to the Java language specification (JLS) and produces the Java 
code according to the Java specification (JVMS). 
 A Java compiler is a compiler for the java programming language. The 
most common way to output a Java compiler is Java class files that 
contain Java platform bytecode neutral, but there are also compilers that 
provide native machine code optimized for a particular combination of 
hardware / operating system. 
 Garbage collection You can at any time. Ideally, this will occur when a 
program is inactive. It is guaranteed to be triggered if there is enough free
memory in the heap to allocate a new object; This can cause a program to
stop momentarily. Explicit memory management is not possible in Java.
Class Data Sharing:
The purpose of this feature is to improve the space occupied by the boot and to 
extend the existing "CDS" (Class-Data Sharing) feature to allow application 
classes to be placed in the shared file. 
The shared data class, introduced in JDK 5, a set of classes is preprocessed in a 
shared file, which can be assigned in the memory at run time to reduce the start 
time. It can also reduce the dynamic memory footprint when several JVMs 
share the same file. 
Currently, the CDS only allows the boot class loader to load the archived 
classes. The CDS of the application allows the class loader of the integrated 
system, the class loader of the integrated platform and the custom class loaders 
to load the archived classes.