Reverse Number using Java

This program prints reverse of a number i.e. if the input is 4321 then output will be 1234.

/*
  Reverse Number using Java
 
*/
package in.blogspot.java2bigdata 
public class ReverseNumberDemo {
 
        public static void main(String[] args) {
               
                int number = 4321;
                int reversedNumber = 0;
                int temp = 0;
               
                while(number > 0){
                       
                        //use modulus operator to strip off the last digit
                        temp = number%10;
                       
                        //create the reversed number
                        reversedNumber = reversedNumber * 10 + temp;
                        number = number/10;
                         
                }
               
                //output the reversed number
                System.out.println("Reversed Number is: " + reversedNumber);
        }
}
 
/*
Output of this Number Reverse program would be
Reversed Number is: 1234
*/

What is a Java Literal ?

Literals:  Any constant value which can be assigned to the variable is called literal.Literals represent numerical (integer or floating-point), character, boolean or string values.

Example:
int literal = 100;
here the value 100 considered as a literal,int is datatype and literal is identifier.

Integral Literals: For the integral data types (byte, short, int and long) we can specify literal value in the following ways.

1. Decimal literals: Allowed digits are 0 to 9.
 Example:  int x=10;

Array Creation

In previous post, we learned more about Array Declarations. In this blog post, I will discuss Array Creation.

Array in java is an object hence we can create by using new keyword.

int[] arr = new int[5];

For every array type corresponding classes are available but these classes are part of java language and not available to the programmer level.

Rule 1: At the time of array creation compulsory we should specify the size otherwise we will get compile time error.

Example:
int[] a=new int[3];
int[] a=new int[];    //C.E:array dimension missing

Rule 2: It is legal to have an array with size zero in java.
Example:
int[] a=new int[0];
System.out.println(a.length); //0

Rule 3: If we are taking array size with -ve int value then we will get runtime exception saying NegativeArraySizeException.

Example:
int[] a=new int[-3];//R.E:NegativeArraySizeException

Rule 4: The allowed data types to specify array size are byte, short, char, int. By mistake if we are using any other type we will get compile time error.

Examples:
int[] a=new int['a'];//(valid)
byte b=10;
int[] a=new int[b];//(valid)
short s=20;
int[] a=new int[s];//(valid)
int[] a=new int[10l];//C.E:possible loss of precision//(invalid)
int[] a=new int[10.5];//C.E:possible loss of precision//(invalid)

Rule 5:  The maximum allowed array size in java is maximum value of int size [2147483647].

Examples:
int[] a1=new int[2147483647];(valid)
int[] a2=new int[2147483648]; //C.E:integer number too large: 2147483648(invalid)