How To Check Whether a Number is a Unique Number or Not in Java?

Unique number can be defined as a number which does not have a single repeated digit in it. Simply it means all the digits of that number are unique digits, no duplicate digits are there in that number.

In this article we will see how to check whether a number is a unique number or not by using Java programming language.

To show you some instances

Instance-1

Input number is 145

Let’s check it by using the logic of unique number −

The digits are 1, 4, 5, all are unique digits.

Hence, 145 is a unique number.

Instance-2

Input number is 37

Let’s check it by using the logic of unique number −

The digits are 3, 7, all are unique digits.

Hence, 37 is a unique number.

Instance-3

Input number is 377

Let’s check it by using the logic of unique number −

The digits are 3, 7, 7 all are not unique digits.

Hence, 377 is not a unique number.

Some other examples of unique numbers include 132, 1, 45, 98, 701, 5, 12, 1234 etc.

Algorithm

Algorithm 1

• Step 1 − Get an integer number either by initialization or by user input.

• Step 2 − Take an outer while loop and get the rightmost digit.

• Step 3 − Take another inner while loop to compare the rightmost digit of step-1 with the leftmost digits. If at any point digits match, the given number has repeated digits. Hence print the given number is not unique and repeat step-2 and step-3 till step-2 covers each digit of the number.

• Step 4 − At last, if no matches are found then print the given number is unique.

Algorithm 2

• Step 1 − Get an integer number either by initialization or by user input.

• Step 2 − Take one outer for loop to iterate each digit one by one.

• Step 3 − Take an inner for loop and compare the leftmost digit of outer for loop with all rightmost digits of inner loop. If at any point digits matches means the given number has repeated digits. Hence print the given number is not unique and repeat step-2 and step-3 till step-2 covers each digit of the number.

• Step 4 − At last, if no matches are found then print the given number is unique.

Multiple Approaches

We have provided the solution in different approaches.

• By Comparing Each Digit Manually

• By Using User String

Let’s see the Java program along with its output one by one.

Approach-1: By Comparing Each Digit Manually

In this approach one integer value will be initialized in the program and then by using the Algorithm-1 we can check whether a number is a unique number or not.

Example

public class Main{
   //main method
   public static void main(String[] args){
   
      //Declared an integer variable and initialized a number as value
      int originalNumber = 123;
      
      //printing the given number to be checked
      System.out.println("Given number: "+originalNumber);
      
      //keep a copy of original number
      int copyOfOriginalNumber = originalNumber;
      
      //initializing count as 1
      int count =0;
      
      //compare each digit with others
      //we will start comparing from rightmost digit with leftmost digits
      while (originalNumber > 0){
      
         //get the rightmost digit
         int digit = originalNumber % 10;
         
         //remove the rightmost digit and get the updated number
         originalNumber = originalNumber / 10;
         
         //assign the updated original number(rightmost digit removed) to a temp variable
         int temp = originalNumber;
         
         //check if the rightmost digit matches with leftmost digits
         while (temp > 0){
         
            //if rightmost digit matches with any leftmost digit then
            //increment count value
            //and break
            if (temp % 10 == digit){
               count = 1;
               break;
            }
            
            //remove rightmost digit from temp
            //and get updated temp value
            temp = temp / 10;
         }
      }
      //if count value is 1 then print given number is unique number
      if (count == 0){   
         System.out.println(copyOfOriginalNumber+" is a unique number");
      }
      
         //else print given number is not a unique number
      else {
         System.out.println(copyOfOriginalNumber+" is not a unique number");
      }
   }
}

Output

Given number: 123
123 is a unique number

Approach-2: By Using String

In this approach one integer value will be initialized in the program and then by using the Algorithm-2 we can check whether a number is a Peterson number or not.

Example

public class Main{
   //main method
   public static void main(String[] args){
   
      //Declared an integer variable and initialized a number as value
      int originalNumber = 7890;
      
      //printing the given number to be checked
      System.out.println("Given number: "+originalNumber);
      
      //initialize count as 0
      int count = 0;
      
      //convert integer to String by using toString() method
      String st = Integer.toString(originalNumber);
      
      //Find length of String by using length() method
      int length=st.length();
      
      //check if the leftmost digit matches with rightmost digits
      for(int i=0;i<length-1;i++){
         for(int j=i+1;j<length;j++){
         
            //if matches then increment count and break
            if(st.charAt(i)==st.charAt(j)){
               count++;
               break;
            }
         }
      }
      //if count value is 1 then print given number is unique number
      if (count == 0){
         System.out.println(originalNumber+" is a unique number");
      }
      
         //else print given number is not a unique number
      else {
         System.out.println(originalNumber+" is not a unique number");
      }
   }
}

Output

Given number: 7890
7890 is a unique number

In this article, we explored how to check a number whether it is a unique number or not in Java by using different approaches.