Nullsafe Long valueOf

Question

Imagine the following scenario Long critId = Long.valueOf(criteriaIdentifier);

If the view is initially loaded criteriaIdentifier may be null, afterwards I set the value depending of the selectedItem in the JSF View.

However, Long.valueOf(criteriaIdentifier) throws a NumberFormatException - If the string cannot be parsed as a long(ie null ).

I've thought of default setting the Id to default -1 , but I wanted to know if there is better practice .

PS: technically the criteriaIdentifier can't be -1, since these values are set from the Database, with a Sequence Generator, so I should know -1 was the default value and properly do the default operations

Answer 1

You can use the NumberUtils from Apache Commons. It's null-safe and you can optionally specify a default value.

Example:

NumberUtils.toLong(null) = 0L
NumberUtils.toLong("")   = 0L
NumberUtils.toLong("1")  = 1L

NumberUtils.toLong(null, 1L) = 1L
NumberUtils.toLong("", 1L)   = 1L
NumberUtils.toLong("1", 0L)  = 1L

For more info, check the API .

Answer 2

Long.valueOf(null) will throw NumberFormatException , not NullPointerException .

In Java 8, you have the possibility to declaratively choose a default evaluation for a nullable inline, eg

Long.valueOf(
    Optional.ofNullable(criteriaIdentifier).orElseGet(() -> "-1")
)

It's a little verbose, but will allow you to default to -1l if criteriaIdentifier is null (no need for additional dependencies).

API here and here .

Answer 3

I'm assuming criteriaIdentifier is a String. You could use org.apache.commons.lang3.math.NumberUtils.toLong(String, long) which gives you the default value if the String argument is null. Or you use org.apache.commons.lang3.math.NumberUtils.toLong(String) which returns zero if the String is null.

Answer 4

It depends on your scenario but usually there are ways to avoid such problems.

Generally setting IDs to -1 is a common practice but I don't think it is a good one. You know that -1 is not a possible value in your scenario but considering just the type Long it is a valid value. So everywhere in the code you will need to implement tests like if id!=-1 which makes the code harder to understand and generally the null value is more suitable for that scenario - Long object without a value.

If it was up to me for example in the method that receives an ID and waits a valid ID if I get null I would throw an exception and let the caller of the method handle that. If it is a web API for example (otherwise why would you get a String?) then you can throw an HTTP error. Or if you want to handle bad arguments then you better return null or use null as default value.

Answer 5

When we say nullSafe we usually desire to receive a null from the api when passing null through it, not a 0 or -1 or any other value.

For this, use createLong static method of the org.apache.commons.lang3.math.NumberUtils .

CAUSION*: This throws NumberFormatException if the input String is NOT null and is NOT numeric.

CAUSION**: since 3.1 it handles hex (0Xhhhh) and octal (0ddd) notations. NB a leading zero means octal; spaces are not trimmed.

Sample:

NumberUtils.createLong(null) --> null
NumberUtils.createLong("1") --> 1
NumberUtils.createLong("hi") --> NumberFormatException
NumberUtils.createLong(" 11") --> NumberFormatException (does not trim)
NumberUtils.createLong("023") --> 19 (leading 0 means octal)
NumberUtils.createLong("0x23") --> 35 (leading 0x means hex)