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From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: getFibonacciArray() cannot call getFibonacciArray(int from)
Date: Wed, 31 Jul 2019 11:52:43 +0200
Organization: Decebal Computing
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I have the following code I use in jshell:
    long[] getFibonacciArray() {
        return getFibonacciArray(0);
        // return getFibonacciStreamFrom(0).toArray();
    }

    long[] getFibonacciArray(int from) {
        return getFibonacciStreamFrom(from).toArray();
    }

    long[] getFibonacciArray(int from, int to) {
        // check parameters
        int count = to - from;
        return getFibonacciStreamFrom(from).limit(count).toArray();
    }

    // Needs at least Java 9 because we use a predicate in the iterator
    // Index 0 of stream i element always contains fibonacci(i) and
    // index 1 always contains fibonacci(i + 1)
    // So the map makes sure you have the fibonacci number
    LongStream getFibonacciStream() {
        return Stream.
            iterate(new long[]{0, 1}, t -> t[0] >= 0, t -> new long[]{t[1], t[0] + t[1]})
            .mapToLong(t -> t[0]);
    }

    LongStream getFibonacciStreamFrom(int from) {
        // Check parameter
        return getFibonacciStream().skip(from).map(l -> l);
    }

When I call this with:
    jshell --startup DEFAULT ~/Java/Jshell/test.jsh

I get:
    |  Error:
    |  method getFibonacciArray in class  cannot be applied to given types;
    |    required: no arguments
    |    found: int
    |    reason: actual and formal argument lists differ in length
    |      return getFibonacciArray(0);
    |             ^---------------^
    |  Error:
    |  cannot find symbol
    |    symbol:   class 
    |  LongStream getFibonacciStreamFrom(int from) {
    |  ^
    |  Error:
    |  static import only from classes and interfaces
    |  LongStream getFibonacciStreamFrom(int from) {
    |  ^
    |  Welcome to JShell -- Version 9-Debian
    |  For an introduction type: /help intro

When I turn it into a class it becomes really strange. I changed the
code to:
    import java.util.stream.LongStream;
    import java.util.stream.Stream;


    class Fibonacci {
        long[] getFibonacciArray() {
            // return getFibonacciArray(0);
            return getFibonacciStreamFrom(0).toArray();
        }

        long[] getFibonacciArray(int from) {
            return getFibonacciStreamFrom(from).toArray();
        }

        long[] getFibonacciArray(int from, int to) {
            // check parameters
            int count = to - from;
            return getFibonacciStreamFrom(from).limit(count).toArray();
        }

        // Needs at least Java 9 because we use a predicate in the iterator
        // Index 0 of stream i element always contains fibonacci(i) and
        // index 1 always contains fibonacci(i + 1)
        // So the map makes sure you have the fibonacci number
        LongStream getFibonacciStream() {
            return Stream.
                iterate(new long[]{0, 1}, t -> t[0] >= 0, t -> new long[]{t[1], t[0] + t[1]})
                .mapToLong(t -> t[0]);
        }

        LongStream getFibonacciStreamFrom(int from) {
            // Check parameter
            return getFibonacciStream().skip(from).map(l -> l);
        }
    }

When compiling this, I get:
    Fibonacci.java:26: error: method iterate in interface Stream<T#2> cannot be applied to given types;
            return Stream.
                         ^
      required: T#1,UnaryOperator<T#1>
      found: long[],(t)->t[0] >= 0,(t)->new l[...]t[1]}
      reason: cannot infer type-variable(s) T#1
        (actual and formal argument lists differ in length)
      where T#1,T#2 are type-variables:
        T#1 extends Object declared in method <T#1>iterate(T#1,UnaryOperator<T#1>)
        T#2 extends Object declared in interface Stream
    1 error

So it has no problem with the method:
    long[] getFibonacciArray()

instead it has a problem with:
    LongStream getFibonacciStream()


What is happening here?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof