Java Basic Syntax - Java

What is the basic Syntax of java?

When we consider a Java application, it could be defined as a group of objects that communicate via invoking each differing’s strategies. Let us now briefly look at what do class, item, methods, and instance variables suggest.

  • Object − objects have states and behaviors. Example: A dog has states - color, name, breed in addition to conduct which includes wagging their tail, barking, ingesting. An item is an example of a class.
  • Class − a class can be defined as a template/blueprint that describes the behavior/state that the item of its type supports.
  • Methods − a method is basically a behavior. a class can contain many methods. it is in methods where the logics are written, facts are manipulated and all the actions are finished.
  • Instance Variables − every object has its specific set of instance variables. An object's state is created by the values assigned to these example variables.

First Java Program

Let us look at a simple code that will print the words Hello World.

Example

Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps −

  • Open notepad and add the code as above.
  • Save the file as: MyFirstJavaProgram.java.
  • Open a command prompt window and go to the directory where you saved the class. Assume it's C:\.
  • Type 'javac MyFirstJavaProgram.java' and press enter to compile your code. If there are no errors in your code, the command prompt will take you to the next line (Assumption : The path variable is set).
  • Now, type ' java MyFirstJavaProgram ' to run your program.
  • You will be able to see ' Hello World ' printed on the window.

Output

Basic Syntax

About Java programs, it is very vital to maintain in mind the following points.

  • Case Sensitivity − Java is case sensitive, which means identifier hello and hello might have a distinct meaning in Java.
  • Class Names − for all class names, the first letter should be in upper Case. If several words are used to form a name of the class, each inner word's first letter have to be in upper Case.
    • Example: class MyFirstJavaClass
  • Method Names − All approach names must begin with a lower Case letter. If several words are used to form the name of the method, then every inner word's first letter have to be in upper Case.
    • Example: public void myMethodName()
  • The program file name − call of the program file should exactly match the class name.
  • When saving the file, you should save it using the class name (recollect Java is case sensitive) and append '.java' to the end of the call (if the filename and the class name do not suit, your application will now not compile).
    • Example: assume 'MyFirstJavaProgram' is the class name. Then the file needs to be saved as 'MyFirstJavaProgram.java'
  • Public static void major (String args[]) − Java application processing begins from the main() method which is a mandatory part of each Java software.

Java Identifiers

All Java components require names. Names used for classes, variables, and methods are called identifiers.
In Java, there are several points to remember about identifiers. They are as follows −

  • All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_).
  • After the first character, identifiers can have any combination of characters.
  • A key word cannot be used as an identifier.
  • Most importantly, identifiers are case sensitive.
  • Examples of legal identifiers: age, $salary, _value, __1_value.
  • Examples of illegal identifiers: 123abc, -salary.

Java Modifiers

Like other languages, it is possible to modify classes, methods, etc., by using modifiers. There are two categories of modifiers −

  • Access Modifiers − default, public , protected, private
  • Non-access Modifiers − final, abstract, strictfp

We will be looking into more details about modifiers in the next section.

Java Variables

Following are the types of variables in Java −

  • Local Variables
  • Class Variables (Static Variables)
  • Instance Variables (Non-static Variables)

Java Arrays

Arrays are objects that store multiple variables of the equal kind. however, an array itself is an object on the heap. we will look into how to declare, construct, and initialize in the upcoming chapters.

Java Enums

Enums had been delivered in Java 5.0. Enums limit a variable to have one in all only a few predefined values. The values in this enumerated list are called enums.

With the use of enums, it is possible to reduce the range of bugs to your code.

for instance, if we remember an application for a fresh juice store, it would be viable to restriction the glass size too small, medium, and huge. this will make certain that it would not allow anyone to order any length other than small, medium, or large.

Example

he above example will produce the following result −

Output

Note − Enums can be declared as their own or inside a class. Methods, variables, constructors can be defined inside enums as well.

Java Keywords

The following list shows the reserved words in Java. These reserved words may not be used as constant or variable or any other identifier names.

abstract

assert

boolean

break

byte

case

catch

char

class

const

continue

default

do

double

else

enum

extends

final

finally

float

for

goto

if

implements

import

instanceof

int

interface

long

native

new

package

private

protected

public

return

short

static

strictfp

super

switch

synchronized

this

throw

throws

transient

try

void

volatile

while

Comments in Java

Java supports single-line and multi-line comments very similar to C and C++. All characters available inside any comment are ignored by Java compiler.

Example

87725459

Output

Using Blank Lines

A line comprising only white space, perhaps with a comment, is known as a blank line, and Java completely ignores it.

Inheritance

In Java, classes can be derived from classes. Basically, if you need to create a new class and here is previously a class that has some of the code you require, and then it is possible to derive your new class from the already existing code.

This concept allows you to reuse the fields and methods of the existing class without having to rewrite the code in a new class. In this scenario, the existing class is called the superclass and the derived class is called the subclass.

Interfaces

In Java language, an interface can be defined as a contract between objects on how to communicate with each other. Interfaces play a vital role when it comes to the concept of inheritance.

An interface defines the methods, a deriving class (subclass) should use. But the implementation of the methods is totally up to the subclass.

What is Next?

The next section explains about Objects and classes in Java programming. At the end of the session, you will be able to get a clear picture as to what are objects and what are classes in Java.

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