In short, I have this code, and I'd like to get an specific element of the array using a condition and lambda. The code would be something like this:
Preset[] presets = presetDALC.getList();
Preset preset = Arrays.stream(presets).select(x -> x.getName().equals("MyString"));
But obviously this does not work. In C# would be something similar but in Java, how do I do this?
You can do it like this,
Optional<Preset> optional = Arrays.stream(presets)
.filter(x -> "MyString".equals(x.getName()))
.findFirst();
// Check whether optional has element you are looking for
if (optional.isPresent()) {
Preset p = optional.get(); // Get it from optional
}
You can read more about Optional here.
isPresent() and .get() is discouraged as it kills the purpose of using optional.
if-else of isPresent() and then use get().
Like this:
Optional<Preset> preset = Arrays
.stream(presets)
.filter(x -> x.getName().equals("MyString"))
.findFirst();
This will return an Optional which might or might not contain a value. If you want to get rid of the Optional altogether:
Preset preset = Arrays
.stream(presets)
.filter(x -> x.getName().equals("MyString"))
.findFirst()
.orElse(null);
The filter() operation is an intermediate operation which returns a lazy stream, so there's no need to worry about the entire array being filtered even after a match is encountered.
Do you want first matching, or all matching?
String[] presets = {"A", "B", "C", "D", "CA"};
// Find all matching
List<String> resultList = Arrays.stream(presets)
.filter(x -> x.startsWith("C"))
.collect(Collectors.toList());
System.out.println(resultList);
// Find first matching
String firstResult = Arrays.stream(presets)
.filter(x -> x.startsWith("C"))
.findFirst()
.orElse(null);
System.out.println(firstResult);
Output
[C, CA]
C
Preset found = Stream.of(presets)
.filter(p -> p.getName().equals("MyString"))
.findFirst().orElseThrow();
Avoid declaring Optional<>, that returned from findFirst as a variable or a parameter. It is designed for return types / "one-liner" styles.
...findFirst().orElse(MY_EMPTY_OBJ);. See: docs.oracle.com/javase/9/docs/api/java/util/…