This question already has answers here:
How to convert Optional<Object> to Optional<String> [closed]
(3 answers)
Closed 2 years ago.
I am trying to convert a set to string inside Optional.OfNullable method like:
test.setAbc(Optional.ofNullable(rule.getSampleSet().toString()).orElse(null));
but if sampleSet is null it will give me a NullPointerException.
can anyone tell me how to resolve this issue using .map method with Optional?
I know one traditional way of doing it by checking nullability beforehand:
if(rule.getSampeSet != null)
but I am much interested in knowing if we can do it in one line.
Instead of calling toString() inside the ofNullable, you could map the optional to it:
test.setAbc(Optional.ofNullable(rule.getSampleSet()).map(Object::toString).orElse(null));
Related
This question already has answers here:
Check chains of "get" calls for null
(11 answers)
Closed 1 year ago.
So I have something that looks like this:
(String) loginResponse.getGroup().getAdditionalProperties().get(something);
and each and every component of the expression could return null. I want to avoid throwing an exception and checking if null after each call doesn't look like the best way to do it:
temp= loginResponse.getGroup();
if(temp!=null){
temp= temp.getAdditionalProperties()
if(temp!=null){
temp.get(something)
}
}etc...
What's a better way to do this?
Thanks
you can use "Optional" and chain the call inside a map()
Optional.ofNullable(toto).map(A::getB).map(B::getC).orElseThrow(...)
Optional.ofNullable(toto).map(A::getB).map(B::getC).orElseGet(...)
You avoid nullPointerException by this way. It goes in the orElse... if anly element is null at any places
This question already has answers here:
Avoiding NullPointerException in Java
(66 answers)
Closed 2 years ago.
I have one complex object just like this;
Object A
Object B
Object C
Object D
property A
property B
So If I need to show the property A in my view, I need to
A.getB().getC().getD().getPropertyA();
but what if my user doesn`t send the object C?
so I need to create one If for every object
if(A.getB() != null){
if(A.getB().getC() != null){
if(A.getB().getC().getD() != null){
//here I can show the propertyA
}
}
}
now I have to show this property in 3 views
There is a better way to does this? a framework or something like this to solve this problem?
You can use Optional.ofNullable and map:
Optional.ofNullable(A.GetB())
.map(B::getC)
.map(C::getD)
.map(D::getPropertyA)
.orElseThrow()
P.S.1: Some developers (and linters) find this approach a code smell, but I think it's more readable that way.
P.S.2: You can use a default value with .orElse instead of .orElseThrow.
This question already has answers here:
Sonar : Replace this lambda with a method reference
(4 answers)
Closed 4 years ago.
I actually wanted to replace this to method reference since sonar is throwing an issue ,I have also searched answers for similar tittle i was't able to find the solution.
String type="test2"
List<String> validSimtSwType = Arrays.asList("test1", "test2", "test3", "test4");
if((validSimtSwType.stream().anyMatch(name -> type.contains(name)))){
//statements
}
You can replace it with a method reference referencing the contains method of the type instance:
if((validSimtSwType.stream().anyMatch(type::contains)))
This question already has answers here:
Check chains of "get" calls for null
(11 answers)
Null check chain vs catching NullPointerException
(19 answers)
Closed 4 years ago.
New to Java.
I'm trying to avoid NullPointerException when iterating over a list. CollectionUtils.emptyIfNull() helps, but not for a chained object.
For example:
for (MyObject myObj : CollectionUtils.emptyIfNull(
result.item.getMyObject().getObjects())) {
// do stuff
}
I have no control over MyObject because I wrote a client that consumes this as a dependency. Any of these attributes could be null, and emptyIfNull() only protects against getObjects() returning null.
Is there a way to apply emptyIfNull() or something similar to the entire chain of calls?
Thanks for the help!
This question already has answers here:
Null check in Java 8 Elvis operator?
(2 answers)
Closed 5 years ago.
I have a situation where I need get the property of a Java object if the object exists or null.
Something like foo == null ? null : foo.bar
Is there an operator available in java to do the same?
No, there is no propagate null operator in Java, cf. C# for example, which does have one. (It was a proposal at some point in Java's evolution, but has not sadly yet been incorporated into the language: foo = foo?.bar would be an obvious notation.)
You need to write this out longhand, as you have done.