Why Are Different Strings Producing the Same UUID Result?

What causes two different strings to yield the same UUID when parsed?

public static void main(String[] args) {
    try {
        UUID t1 = UUID.fromString("38e1036d-7527-42a3-98ca-f2f19d3155db");
        UUID t2 = UUID.fromString("123438e1036d-7527-42a3-98ca-f2f19d3155db");
        System.out.println(t1.toString().equals(t2.toString()));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

When different strings yield the same UUID after parsing, it's usually due to an issue in the strings' formatting or content, particularly if they exceed proper UUID length.

public static void main(String[] args) {
    try {
        UUID t1 = UUID.fromString("38e1036d-7527-42a3-98ca-f2f19d3155db");
        UUID t2 = UUID.fromString("123438e1036d-7527-42a3-98ca-f2f19d3155db");
        // Check if UUIDs refer to the same instance
        System.out.println(t1.equals(t2)); // Should be false
    } catch (IllegalArgumentException e) {
        System.out.println("Invalid UUID format: " + e.getMessage());
    }
}

Causes

• UUIDs are 128-bit numbers represented as 36-character strings, including hyphens. If an input exceeds this format or contains invalid characters, the UUID parser may misinterpret it.
• In your example, the second string exceeds the expected UUID structure and might be truncated or altered when parsed.

Solutions

• Ensure both strings conform strictly to the UUID format: 8-4-4-4-12 hexadecimal digits.
• If necessary, validate or clean up the strings before attempting to convert them to UUIDs.

Mistake: Ignoring UUID format specifications.

Solution: Always validate that strings adhere to the 8-4-4-4-12 character format.

Mistake: Assuming similar but different UUIDs will parse correctly without checking inputs.

Solution: Use try-catch blocks to handle potential UUID parsing exceptions.