Java By Kiran
Java Training Institute in Pune
Java Training Institute in Pune
Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.
Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX/Linux like HP-Unix, Sun Solaris, Redhat Linux, Ubuntu, CentOS, etc.
It’s compiler generates an architecture-neutral object file format, which makes the compiled code to be executable on many processors, with the presence of Java runtime system.
Some features include Object Oriented, Platform Independent, Robust, Interpreted, Multi-threaded
Java uses Just-In-Time compiler to enable high performance. Just-In-Time compiler is a program that turns Java bytecode, which is a program that contains instructions that must be interpreted into instructions that can be sent directly to the processor.
It is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.
When Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. This byte code is distributed over the web and interpreted by virtual Machine (JVM) on whichever platform it is being run.
Netbeans, Eclipse, etc.
Some Java keywords are import, super, finally, etc.
Object is a runtime entity and it’s state is stored in fields and behavior is shown via methods. Methods operate on an object's internal state and serve as the primary mechanism for object-to-object communication.
A class is a blue print from which individual objects are created. A class can contain fields and methods to describe the behavior of an object.
A class consist of Local variable, instance variables and class variables.
Variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and it will be destroyed when the method has completed.
Instance variables are variables within a class but outside any method. These variables are instantiated when the class is loaded.
These are variables declared with in a class, outside any method, with the static keyword.
An Object is first declared, then instantiated and then it is initialized.
Default value of byte datatype is 0.
Default value of float and double datatype in different as compared to C/C++. For float its 0.0f and for double it’s 0.0d
This data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an int.
Postfix operators i.e ( ) [ ] . is at the highest precedence
Variables used in a switch statement can only be a byte, short, int, or char.
This method is used to get the primitive data type of a certain String.
The following shows the explanation individually:
• public: it is the access specifier.
• static: it allows main() to be called without instantiating a particular instance of a class.
• void: it affirms the compiler that no value is returned by main().
• main(): this method is called at the beginning of a Java program.
• String args[ ]: args parameter is an instance array of class String
Java Runtime Environment is an implementation of the Java Virtual Machine which executes Java programs. It provides the minimum requirements for executing a Java application;
JAR files is Java Archive fles and it aggregates many files into one. It holds Java classes in a library. JAR files are built on ZIP file format and have .jar file extension.
This is Web Archive File and used to store XML, java classes, and JavaServer pages. which is used to distribute a collection of JavaServer Pages, Java Servlets, Java classes, XML files, static Web pages etc.
It improves the runtime performance of computer programs based on bytecode.
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.