By definition foreach loop requires an Iterable to be passed in. It can be achieved with anonymous class: for (String s : new Iterable<String>() { @Override public Iterator<String> iterator() { return stream.iterator(); } }) { writer.append(s); } This can be simplified with lambda because Iterable is a functional interface: for (String s : (Iterable<String>) () … Read more
The documentation of LocalDateTime specifies the instance of LocalDateTime is immutable, for example plusHours public LocalDateTime plusHours(long hours) Returns a copy of this LocalDateTime with the specified number of hours added. This instance is immutable and unaffected by this method call. Parameters: hours – the hours to add, may be negative Returns: a LocalDateTime based … Read more
PermGen is replaced with Metaspace in Oracle/Sun JDK8, which is very similar. The main difference is that Metaspace can expand at runtime.
Why with streams? You just have to get a random number from 0 to the size of the list and then call get on this index: Random r = new Random(); ElementType e = list.get(r.nextInt(list.size())); Stream will give you nothing interesting here, but you can try with: Random r = new Random(); ElementType e = … Read more
Extend the java API with a method to unwrap Optional: fun <T> Optional<T>.unwrap(): T? = orElse(null) Then use it like you wanted: val msg: Something? = optional.unwrap() // the type is enforced See https://kotlinlang.org/docs/reference/extensions.html for details.
Yes, it’s called scala-java8-compat, and here’s the method you’re looking for.
What you have here, is a follow-up error which masks the original error. When lambda instances are serialized, they use writeReplace to dissolve their JRE specific implementation from the persistent form which is a SerializedLambda instance. When the SerializedLambda instance has been restored, its readResolve method will be invoked to reconstitute the appropriate lambda instance. … Read more
What you have here, is a follow-up error which masks the original error. When lambda instances are serialized, they use writeReplace to dissolve their JRE specific implementation from the persistent form which is a SerializedLambda instance. When the SerializedLambda instance has been restored, its readResolve method will be invoked to reconstitute the appropriate lambda instance. … Read more
If you use JPA 2.1 this is simple to do. Converters allow your JPA entities to use the new java.time.LocalDate and java.time.LocalDateTime classes. Simply define the needed converter classes: LocalDatePersistenceConverter.java import java.time.LocalDate; import javax.persistence.AttributeConverter; import javax.persistence.Converter; @Converter public class LocalDatePersistenceConverter implements AttributeConverter<LocalDate, java.sql.Date> { @Override public java.sql.Date convertToDatabaseColumn(LocalDate entityValue) { if (entityValue != null) { … Read more
To answer the second part of your question, if you want to avoid the exception when the list is empty and return some double value, use orElse instead of getAsDouble: return weightChanges.stream() .mapToDouble(WeightChange::getValue) .average() .orElse(Double.NaN);