OTP Generation for Payment System Using Supplier Functional Interface

OTP Generation for Payment System Using Supplier Functional Interface | Java 8 Real-Time Project

July 26, 2026

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package org.practice.basicprgms;

public class SupplierPaymentDemo {

	public static void main(String[] args) {
		Customer customer = new Customer("Rahul", "9884715428", 50000);		
		PaymentService.processPayment(customer, 15000);
	}
}

package org.practice.basicprgms;

import java.util.Scanner;
import java.util.UUID;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.Supplier;

public class PaymentService {

	public static Supplier<String> otpSupplier = () ->
		String.valueOf(ThreadLocalRandom.current().nextInt(100000,999999));
		
	public static Supplier<String> transactionSupplier = () ->
		"TXN - "+ UUID.randomUUID().toString().substring(0, 8).toUpperCase();
		
	public static Supplier<String> invoiceSupplier = () ->
		"INV - "+ UUID.randomUUID().toString().substring(0, 6).toUpperCase();
	
	public static void processPayment(Customer customer, double amount) {
		if(amount <= 100) {
			System.out.println("Minimum Payment must be 100");
			return;
		}
		
		if(customer.getAccountBalance() < amount) {
			System.out.println("Insufficient Balance");
			return;
		}
		
		String generatedOTP = otpSupplier.get();
		System.out.println("Sending OPT on this Number : "+ customer.getMobileNumber());
		
		System.out.println("Generated OTP : "+ generatedOTP);
		// Here we have to integrate sms gateway to send the OTP On customer mobile number;
		
		System.out.println("Pleaes Enter your OTP here :");
		Scanner scanner = new Scanner(System.in);
		String enteredOTP = scanner.nextLine().trim();
		
		if(!generatedOTP.equals(enteredOTP)) {
			System.out.println("Invalid OTP");
			return;
		}
		
		customer.setAccountBalance(customer.getAccountBalance() - amount);
		
		String transactionNumber = transactionSupplier.get();
		
		String invoiceNumber = invoiceSupplier.get();
		
		System.out.println("\n========== PAYMENT SUCCESS ==========");

		System.out.println("Customer      : " + customer.getName());
		System.out.println("Amount Paid   : " + amount);
		System.out.println("TransactionId : " + transactionNumber);
		System.out.println("Invoice No    : " + invoiceNumber);
		System.out.println("Balance Left  : " + customer.getAccountBalance());		
	}
}

package org.practice.basicprgms;

public class Customer {

	private String name;
	private String mobileNumber;
	private double accountBalance;
	
	public Customer() {
		super();
	}

	public Customer(String name, String mobileNumber, double accountBalance) {
		super();
		this.name = name;
		this.mobileNumber = mobileNumber;
		this.accountBalance = accountBalance;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getMobileNumber() {
		return mobileNumber;
	}

	public void setMobileNumber(String mobileNumber) {
		this.mobileNumber = mobileNumber;
	}

	public double getAccountBalance() {
		return accountBalance;
	}

	public void setAccountBalance(double accountBalance) {
		this.accountBalance = accountBalance;
	}
}

output:
Sending OPT on this Number : 9884715428
Generated OTP : 970750
Pleaes Enter your OTP here :
970750

========== PAYMENT SUCCESS ==========
Customer      : Rahul
Amount Paid   : 15000.0
TransactionId : TXN - 22604242
Invoice No    : INV - 0DDC66
Balance Left  : 35000.0