user2116243 :
I have the following code:
private static <T> Map<String, ?> getDifference(final T a, final T b, final Map<String, Function<T, Object>> fields) {
return fields.entrySet().stream()
.map(e -> {
final String name = e.getKey();
final Function<T, Object> getter = e.getValue();
final Object pairKey = getter.apply(a);
final Object pairValue = getter.apply(b);
if (Objects.equals(pairKey, pairValue)) {
return null;
} else {
return Pair.of(name, pairValue);
}
})
.filter(Objects::nonNull)
.collect(Collectors.toMap(Pair::getKey, Pair::getValue));
}
Now, pairValue can be null. In order to avoid the NPE as described here, while "collect"ing, I wish to ensure that I send only those values that are non-null. If null, I want to send "".
So, I tried replacing the last line with this:
.collect(Collectors.toMap(Pair::getKey,Optional.ofNullable(Pair::getValue).orElse(""));
And other modifications thereof:
.collect(Collectors.toMap(pair -> pair.getKey(), Optional.ofNullable(pair -> pair.getValue()).orElse(""));
Does not compile. I'm not sure what is needed here. Any help?
Nikolai Shevchenko :
You have incorrect syntax. toMap()'s second parameter must be lambda, so
.collect(Collectors.toMap(
pair -> pair.getKey(),
pair -> Optional.ofNullable(pair.getValue()).orElse("")
));
OR
you can modify map() section as follows
return Pair.of(name, Optional.ofNullable(pairValue).orElse(""));
and use your original collect()
Guess you like
Origin http://10.200.1.11:23101/article/api/json?id=465842&siteId=1