Short version of check if the result of an object in not null then cast to boolean and set in Java

Question

I have been looking for a short version of the following statement in Java:

if(headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT) !=null ) {
      record
          .setNativeHeadersPresent((boolean) headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT));
    }

If I would like to use Optional.ofNullable it doesn't work as I need to cast the object to boolean as well.

P.S: I am using Java8.

Considering `headers` as a `Map`, another way to resolve things would be `if(headers.containsKey(BinderHeaders.NATIVE_HEADERS_PRESENT)) { record.setNativeHeadersPresent((boolean) headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT)); }`. One doesn't always need an `Optional` to get rid of `null`s in the code. — Naman, Aug 31 '19 at 01:59
You have three possible input conditions for the `NATIVE_HEADERS_PRESENT` value: `true`, `false` and `null`. Are you saying that if the value is `null` you don't want to invoke `record.setNativeHeadersPresent()` at all? Sounds like there's a logic leak there, or bad database design in that something called `NATIVE_HEADERS_PRESENT` does not sound like it should allow a `null` value. — Jim Garrison, Aug 31 '19 at 03:43
@JimGarrison Yes. That's right. NATIVE_HEADERS_PRESENT is a message header that I received from an external party, I cannot be sure that always it is going to be provided. However, the downstream system only accepts 'true' and 'false', so I just want to say that if it doesn't exist, don't set the value as null is not accepted. — Ali, Aug 31 '19 at 08:52
If I understand you, you want to map input {true,false,null} -> {true,false} with both input null and input false mapping to output false. Is that correct? — Jim Garrison, Aug 31 '19 at 16:06

Andrew Tobilko · Accepted Answer · 2019-08-31T10:40:30.847

3

It's not what Optional.ofNullable for, but I will share how it can be done because I love method references.

Optional.ofNullable(headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT))
        .map(boolean.class::cast)
        .ifPresent(record::setNativeHeadersPresent);

Since you've got a Map<String, String>, Map#getOrDefault could be an option.

record.setNativeHeadersPresent(
    Boolean.parseBoolean(
        headers.getOrDefault(BinderHeaders.NATIVE_HEADERS_PRESENT, "false")
    )
);

edited Aug 31 '19 at 10:40

answered Aug 31 '19 at 01:31

Andrew Tobilko

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Do we have any other way of addressing that in Java without using Optional, then? I am a really big fan of if you could do something it doesn't mean you should do it. – Ali Aug 31 '19 at 01:57
@Alin we have control flow statements which are fine in most cases. They keep things simple and to the point. – Andrew Tobilko Aug 31 '19 at 10:12
2

@Alin you may want to use [`Map#getOrDefault`](https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/util/Map.html#getOrDefault(java.lang.Object,V)). I assume you get a String, so it would be `record.setNativeHeadersPresent(Boolean.parseBoolean(headers.getOrDefault(BinderHeaders.NATIVE_HEADERS_PRESENT, "false")));` – Andrew Tobilko Aug 31 '19 at 10:13
@AndrewTobilko `Map#getOrDefault()` returns the default only if the key is not present, but will return `null` if the map permits null values and a null value was associated with the key. – Jim Garrison Sep 01 '19 at 03:52
Why does your second example suddenly assume that the map values are strings? Further mind the difference between calling `setNativeHeadersPresent` when the value is present and always calling `setNativeHeadersPresent`… By the way, it must be `Boolean.class::cast` instead of `boolean.class::cast`, as you can not cast an object to a primitive type. – Holger Sep 02 '19 at 09:35

score 2 · Answer 2 · answered Aug 31 '19 at 16:25

2

You seem to be trying to implement this mapping

Input  ->  Output
-----      ------
true       true
false      false
null       false

If you MUST use Optional, the most succinct way of expressing this is

Optional.ofNullable(headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT)).orElse(false);

However, you don't need Optional at all. The following will do what you are asking for:

Boolean nhp = headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT);
record.setNativeHeadersPresent((nhp == null) ? false : nhp);

If you want it in one statement (at the expense of invoking headers.get() twice):

record.setNativeHeadersPresent(
    (headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT) == null) 
        ? false 
        : headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT));

Important Note: The use of Map#getOrDefault(...,false) may not work. If the Map implementation supports null values, then getOrDefault() can still return null if a null value was associated with that key. (i.e. at some point put(key,value) with value==null was executed). The default value is returned only if the key was not present in the map.

answered Aug 31 '19 at 16:25

Jim Garrison

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I appreciate your approach using a conditional expression. With all the fuss about functional programming in Java, ppl. tend to miss that a conditional expression **is** the functional equivalent of if-else :) – Stephan Herrmann Aug 31 '19 at 19:04
Thanks for your answer. The only thing is the Map is a type of and I need to cast it to boolean as well. – Ali Sep 01 '19 at 00:50
1

@Alin If you really cannot narrow down the value type beyond just `Object` then you also need to handle the case where the value cannot be converted to `boolean`. I presume you want `false` then. Other than that this approach still works, you just have to test for type compatibility as well as `null`. – Jim Garrison Sep 01 '19 at 03:55
@StephanHerrmann still, any compound boolean expression containing a `boolean` literal can be expressed without. So instead of `(nhp == null) ? false : nhp`, you can simply use `nhp != null && nhp`. – Holger Sep 02 '19 at 09:39
@Alin then, simplest solution: `record.setNativeHeadersPresent(Boolean.TRUE.equals(headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT)));` – Holger Sep 02 '19 at 09:40

score 0 · Answer 3 · answered Aug 31 '19 at 01:32

If I understand correctly, a simple call to ifPresent should work:

Optional.ofNullable(headers.get(BinderHeaders.NATIVE_HEADERS_PRESENT))
    .ifPresent(
        x -> record.setNativeHeadersPresent((boolean)x)
    )

It doesn't matter what you do with the optional (whether you cast it or not), because ifPresent accepts a "function" as its parameter. You can pass in code that does whatever you like.

Short version of check if the result of an object in not null then cast to boolean and set in Java

3 Answers3