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Introduction to Java

Generate Unique Invoice ID Using Timestamp - Java Program

import java.text.SimpleDateFormat;
import java.util.Date;
 
public class InvoiceIDGenerator {
    public static void main(String[] args) {
       
        // Get current date & time
        Date now = new Date();
 
        // Format the timestamp
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMddHHmmssSSS");
 
        // Generate invoice ID
        String invoiceID = "INV-" + formatter.format(now);
 
        // Display
        System.out.println("Generated Unique Invoice ID: " + invoiceID);
    }
}
 

 
OUTPUT :
Generated Unique Invoice ID: INV-20250112145730987

Explanation

✅ 1. Date now = new Date();

• Creates an object storing the current date and time.
• Every millisecond is unique → good for invoice IDs.

✅ 2. SimpleDateFormat("yyyyMMddHHmmssSSS")

This pattern converts the timestamp into:

- Ensures no two invoice IDs are the same.

✅ 3. invoiceID = "INV-" + formatter.format(now);

• Prefix "INV-" makes the ID clearly recognizable.
• Example:

• INV-20250112145730987

✅ 4. Prints result

Displays the unique invoice number.