1) Program/ Example - Reduce list to store it in Optional in java 8
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
/**
* Write Program to - Reduce list to store it in Optional - in java 8
*/
public class StreamsExample4_ReduceListToStoreInOptional {
public static void main(String[] args) {
List<String> StringList = new ArrayList<>();
StringList.add("a");
StringList.add("b");
StringList.add("a");
// In one line display all distinct records in stream
Stream<String> stream = StringList.stream(); // Convert list (ArrayList) of String to stream
//Reduce list to store it in Optional
System.out.println("1.Reduce list to store it in Optional");
//A container object may or may not contain a non-null value
Optional<String> optional = stream
.sorted() //Sort the stream
.reduce((s1, s2) -> s1 + "," + s2); //reduce() method will reduce stream to - ad,ank,az,neh,sam
//Display optional
System.out.println(optional.isPresent()); //isPresent() will return true - If a value is present
//OR
System.out.println(optional.get()); //get() returns the value.
}
}
/* OUTPUT
1.Reduce list to store it in Optional
true
a,a,b
*/
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