StreamLolz.java

import java.util.stream.*;
import java.util.function.*;

class FMTS {
  public static void main(String[] args) {
    
    IntStream intStream1 = IntStream.of(1, 2);
    IntStream intStream2 = IntStream.of(1, 2);
     
    //FlatMap
    IntStream infinite1 = intStream1.flatMap( i -> IntStream.iterate(i, IntUnaryOperator.identity()) );
    System.out.println(infinite1.findFirst()); //will not terminate
    
    //Map + flatten
    IntStream infinite2 = intStream2.map(i -> IntStream.iterate(i, IntUnaryOperator.identity())).reduce(Stream.empty(), Stream::concat);
    System.out.println(infinite2.findFirst()); //prints Optional[1]
  }
}