Java 8 Optional is Not Just for Replacing a null Value
Java 8 Optional is Not Just for Replacing a null Value
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In Java 8, you can return an Optional instead of return null; as you might do in Java 7. This may or may not make a big difference depending on whether you tend to forget to check for null or whether you use static code analysis to check to nullalbe references.
However, there is a more compelling case which is to treat Optional like a Stream with 0 or 1 values.
Simple Optional Use Case
String text = something();
if (text != null) {
Optional text = something();
if (text.isPresent()) {
String text2 = text.get();
Optional text = something();
if (text != null && text.isPresent()) {
String text2 = text.get();
A more complex example
static String getFirstSecondThird(Nested nested) {
try {
return ((Contained2) nested.first.second).get(0).third;
} catch (NullPointerException |
ClassCastException |
IndexOutOfBoundsException ignored) {
return null;
}
}
static Optional getFirstSecondThird(Optional nested) {
return nested // could be non-present
.map(x -> x.first) // could be null
.map(x -> x.second) // could be null
// could be another type
.map(x -> x instanceof Contained2 ? (Contained2) x : null)
.map(x -> x.list) // could be null
.filter(x -> !x.isEmpty()) // could be empty
.map(x -> x.get(0)) // could be null
.map(x -> x.third); // could be null.
}
Conclusion
Additional
static class Nested {
Contained first;
}
static class Contained {
IContained2 second;
}
interface IContained2 {
}
static class Contained2 implements IContained2 {
List list;
}
static class Data {
String third;
}
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