FULL PRODUCT VERSION :


A DESCRIPTION OF THE PROBLEM :
The javadoc of java.util.stream.Collectors#toMap method starts by referencing the correct java.util.function.Function#identity() method but uses Functions.identity() in the code sample.

     * @apiNote
     * It is common for either the key or the value to be the input elements.
     * In this case, the utility method
     * {@link java.util.function.Function#identity()} may be helpful.
     * For example, the following produces a {@code Map} mapping
     * students to their grade point average:
     * <pre>{@code
     * Map<Student, Double> studentToGPA
     * students.stream().collect(toMap(Functions.identity(),
     * student -> computeGPA(student)));
     * }</pre>
     * And the following produces a {@code Map} mapping a unique identifier to
     * students:
     * <pre>{@code
     * Map<String, Student> studentIdToStudent
     * students.stream().collect(toMap(Student::getId,
     * Functions.identity());
     * }</pre>


REPRODUCIBILITY :
This bug can be reproduced always.