How to Add Leading Zeros to Numbers in Java: Which Method is Best?

How to Add Leading Zeroes to a Number in Java

In Java, there are several ways to add leading zeroes to a number, including:

1. Custom Function**: You can use a custom function to append zeroes to the beginning of a number, as shown in the example code you provided. However, this function may not handle all scenarios, such as when the target number has more digits than the desired leading zero count.

2. String.format: The String.format method allows you to specify a format string that includes a placeholder for the number and a format specifier to add leading zeroes:

In this example, d specifies that the resulting string should contain three characters, with leading zeroes if needed.

3. DecimalFormat: The DecimalFormat class from the java.text package provides a more advanced way to format numbers, including adding leading zeroes:

This approach uses the "000" pattern to specify that the resulting string should have exactly three characters, with leading zeroes as necessary.

4. Apache Commons Lang: The Apache Commons Lang library includes a NumberUtils class that provides methods for converting numbers to strings with leading zeroes:

This method returns a string with at least the specified number of characters, left-padded with zeroes.

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