FULL PRODUCT VERSION :
java version "1.8.0_101"
Java(TM) SE Runtime Environment (build 1.8.0_101-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10586]

EXTRA RELEVANT SYSTEM CONFIGURATION :
Built using Maven 3.3.9

A DESCRIPTION OF THE PROBLEM :
When the method StringBuilder#length is used as a method reference and then executed, java throws a IllegalAccessError. If the method is used as a lambda expression instead, no exception is thrown.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Stream over a collection of StringBuilders using Collection.stream().
Map every StringBuilder to an int using .mapToInt(StringBuilder::length).
Terminate the stream. The exception is now thrown.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Referencing StringBuilder::length should give exactly the same result as the lambda:
    (StringBuilder sb) -> sb.length()

ACTUAL -
An exception is thrown.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.IllegalAccessError: tried to access class java.lang.AbstractStringBuilder from class com.github.pyknic.mavenproject36.Main
        at com.github.pyknic.mavenproject36.Main.lambda$main$0(Main.java:18)
        at java.util.stream.ReferencePipeline$4$1.accept(Unknown Source)
        at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
        at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
        at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
        at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source)
        at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
        at java.util.stream.IntPipeline.reduce(Unknown Source)
        at java.util.stream.IntPipeline.max(Unknown Source)
        at com.github.pyknic.mavenproject36.Main.main(Main.java:19)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
@org.junit.Test
public void test() {
    final int maxLength =
        java.util.stream.Stream.of(
            new StringBuilder("A"),
            new StringBuilder("BB"),
            new StringBuilder("CCC")
        )
        .mapToInt(StringBuilder::length)
        .max().orElse(0); // IllegalAccesException

    org.junit.Assert.assertEquals(3, maxLength);
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Never use the double-colon "::" operator when referencing methods in StringBuilder. Instead, use a lambda expression that invokes the method.

Example:
replace .mapToInt(StringBuilder::length)
with .mapToInt(sb -> sb.length())