Question

Need help answering the following using java

2a. Write a java program (just a “void main”) that will reverse the digits of a user entered, positive three-digit number. You can assume the user enters an integer. Your code segment should first verify that the user has entered a number from 100 to 999 (error message if not). If the user has entered a three-digit number, output a new number with the original digits reversed.

2b. Instead of being limited to a 3 digit number, what if your previosu program had to revierse the digits of any integer? Discuss in detail how you would implement this, code not necessary.

Answer 1

2a)

Program:

import java.util.*;

class ReverseNumber
{
public static void main(String args[])
{
Scanner input=new Scanner(System.in);
int num,rev,rem,i;
rev=0;

System.out.print("\nEnter a number: ");
num=input.nextInt();

if(num>=100 && num<=999)
{
for(i=1;i<=3;i++)
{
rem=num%10;
num=num/10;
rev=rev*10+rem;
}
System.out.println("\nReverse Number: "+rev);
}
else
{
System.out.println("\nPlease enter three digits number only!!");
}
System.out.println("\n");
}
}

Output:

2b)

First, remove the if-else part of the program.

Next, use any loop but most preferable for this example is while loop and here there has to be a condition where the number has to be greater than 0 so while loop will be executed until the value of num becomes zero. and meanwhile, it will remove all the digit from number then store in rev variable.

sample Code:

while(num>0)

{

rem=num%10;

num=num/10;

rev=rev*10+rem

}

then print the value of rev;

Program:

import java.util.*;

class ReverseNumber
{
public static void main(String args[])
{
Scanner input=new Scanner(System.in);
int num,rev,rem;
rev=0;

System.out.print("\nEnter a number: ");
num=input.nextInt();

while(num>0)
{
rem=num%10;
num=num/10;
rev=rev*10+rem;
}
System.out.println("\nReverse Number: "+rev);
System.out.println("\n");
}
}

Output: