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. This tutorial gives a complete understanding of Java. This reference will take you through simple and practical approaches while learning Java Programming language.

Java is a MUST for students and working professionals to become a great Software Engineer specially when they are working in Software Development Domain. I will list down some of the key advantages of learning Java Programming:

• Object Oriented − In Java, everything is an Object. Java can be easily extended since it is based on the Object model.
• Platform Independent - Unlike many other programming languages including C and C++, 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 the Virtual Machine (JVM) on whichever platform it is being run on.
• Simple - Java is designed to be easy to learn. If you understand the basic concept of OOP Java, it would be easy to master.
• Secure - With Java's secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption.

If you are still willing to set up your environment for Java programming language, then this section guides you on how to download and set up Java on your machine. Following are the steps to set up the environment. Java SE is freely available from the link Download Java. You can download a version based on your operating system. Follow the instructions to download Java and run the .exe to install Java on your machine. Once you installed Java on your machine, you will need to set environment variables to point to correct installation directories −

Setting Up the Path for Windows Assuming you have installed Java in c:\Program Files\java\jdk directory − Right-click on 'My Computer' and select 'Properties'. Click the 'Environment variables' button under the 'Advanced' tab. Now, alter the 'Path' variable so that it also contains the path to the Java executable. Example, if the path is currently set to 'C:\WINDOWS\SYSTEM32', then change your path to read 'C:\WINDOWS\SYSTEM32;c:\Program Files\java\jdk\bin'.

byte

• Byte data type is an 8-bit signed two's complement integer
• Minimum value is -128 (-2^7)
• Maximum value is 127 (inclusive)(2^7 -1)
• Default value is 0
• Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an integer.
• Example: byte a = 100, byte b = -50

short

• Short data type is a 16-bit signed two's complement integer
• Minimum value is -32,768 (-2^15)
• Maximum value is 32,767 (inclusive) (2^15 -1)
• Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an integer
• Default value is 0.
• Example: short s = 10000, short r = -20000

A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable. You must declare all variables before they can be used. Following is the basic form of a variable declaration − data type variable [ = value][, variable [ = value] ...] ;

Here data type is one of Java's datatypes and variable is the name of the variable. To declare more than one variable of the specified type, you can use a comma-separated list. Following are valid examples of variable declaration and initialization in Java − int a, b, c; // Declares three ints, a, b, and c.
int a = 10, b = 10; // Example of initialization
byte B = 22; // initializes a byte type variable B.
double pi = 3.14159; // declares and assigns a value of PI.
char a = 'a'; // the char variable a iis initialized with value 'a'

There may be a situation when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Declaration − The newly declared block variable, is of a type compatible with the elements of the array you are accessing. The variable will be available within the for block and its value would be the same as the current array element. Expression − This evaluates to the array you need to loop through. The expression can be an array variable or method call that returns an array.

public class Test {

    public static void main(String args[]) {
        int [] numbers = {10, 20, 30, 40, 50};

        for(int x : numbers ) {
            System.out.print( x );
            System.out.print(",");
        }
        System.out.print("\n");
        String [] names = {"James", "Larry", "Tom", "Lacy"};

        for( String name : names ) {
            System.out.print( name );
            System.out.print(",");
        }
    }
    }
          

Strings, which are widely used in Java programming, are a sequence of characters. In Java programming language, strings are treated as objects. The Java platform provides the String class to create and manipulate strings.

Creating Strings

The most direct way to create a string is to write −

Whenever it encounters a string literal in your code, the compiler creates a String object with its value in this case, "Hello world!'. As with any other object, you can create String objects by using the new keyword and a constructor. The String class has 11 constructors that allow you to provide the initial value of the string using different sources, such as an array of characters.

public class StringDemo {

    public static void main(String args[]) {
        char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.' };
        String helloString = new String(helloArray);
        System.out.println( helloString );
    }
}
          

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