Important Basics of Java Programming Language

- July 30, 2015

Hello Guys....

This is my first post and in this i am going to talk about some of the important basics and concepts of Java Programming Language which are generally ignored by most of us...

I hope that after reading this post many basic concepts regarding java will be cleared to you.So let's get started:-

1. Automatic Type Promotion

Consider this code :-

public class promotion
{
    public static void main(String args[])
    {
        byte a=10;
        byte b=2;
        byte c=a*b;
        System.out.println("Result of 10x2 = "+c);
    }
}

When we run this code in a file named promotion.java we get the error as follows :-

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from int to byte

at promotion.main(promotion.java:7)

So why do we get this error ???? as we know that the range of the byte is 256 and the multiplication of 'a' and 'b' is 20 which is <256 still this error occurs. The Solution to this error is given below :-

public class promotion
{
   public static void main(String args[])
   {
       byte a=10;
       byte b=2;
       byte c=(byte) (a*b); // Altered Code....
       System.out.println("Result of 10x2 = "+c);
   }
}

So what have we done ??? Actually we have typecasted the multiplication of a and b to a byte so that we get the result in byte.
This is a very interesting Property of Java that during the calculations the java language automatically promote the data variables having small data types like - short,char,byte to int this is the reason for that error. So if we want to add a line to our code as -

int d;
d=a*b/5;
System.out.println("Result of 10x2/5 = "+d);

So, in this case we don't have to do any explicit typecasting as the result is calculated in 'int' and stored in 'int', so we get the output as desired...