FULL PRODUCT VERSION :
openjdk version "1.8.0_91"
OpenJDK Runtime Environment (build 1.8.0_91-b14)
OpenJDK 64-Bit Server VM (build 25.91-b14, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux godwit.cs.washington.edu 4.4.6-200.fc22.x86_64 #1 SMP Wed Mar 16 22:13:40 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Creating an instance of an inner class always requires a non-null outer class.

However, it is possible to call Constructor.newInstance() to create an instance of an inner class with a null outer class, at least when the outer class declares no fields.
Please see the below code, which reproduces the error.

Proposed resolution: newInstance for an inner class should throw a NullPointerException whenever the first argument is null.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
javac NullOuterTest.java
java -ea -cp . NullOuterTest

where NullOuterTest.java is in the "Source code" part of this issue report.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expected:
Both calls to invokeReflectively should issue a NullPointerException
ACTUAL -
Actual:
The first call to invokeReflectively completes normally, creating an illegal object.
The second call to invokeReflectively issues a NullPointerException, as desired.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.lang.reflect.*;

class ClassWithInnerClass {
  public class A {
    public String toString() {
      return String.format("ClassWithInnerClass.A(outer=%s)",
                           ClassWithInnerClass.this);
    }
  }
}

class ClassWithInnerClassAndField {
  int i;
  public class A {
    public String toString() {
      return String.format("ClassWithInnerClass.A(outer=%s, i=%s)",
                           ClassWithInnerClassAndField.this, i);
    }
  }
}

public class NullOuterTest {
  public static void main(String[] args) {


    System.out.println("Using reflection:");
    // expected: this first invocation should fail with a NullPointerException
    invokeReflectively(ClassWithInnerClass.class, null);
    // this second invocation correctly fails with a NullPointerException
    invokeReflectively(ClassWithInnerClassAndField.class, null);

    System.out.println("Executing directly:");
    try {
      ClassWithInnerClass outerObj = null;
      ClassWithInnerClass.A a2 = outerObj.new A();
      System.out.println("Created object with null outer: " + a2);
    } catch (NullPointerException e) {
      System.out.println("NPE when creating object with null outer");
    }

  }

  private static void invokeReflectively(Class<?> outerClass, Object outerObj) {
    Constructor<?> c = getInnerConstructor(outerClass);
    System.out.println("Constructor: " + c);
    try {
      Object obj = c.newInstance(outerObj);
      System.out.println("Created object with null outer: " + obj);
    } catch (Throwable e) {
      System.out.printf("failure calling constructor; type=%s; message=%s%n",
                        e.getClass(), e.getMessage());
    }
  }

  private static Constructor<?> getInnerConstructor(Class<?> outerClass) {
    Constructor<?> constructor = null;
    Class<?>[] innerClasses = outerClass.getDeclaredClasses();
    assert innerClasses.length == 1: "should only be one inner class";
    Class<?> innerClass = innerClasses[0];
    try {
      constructor = innerClass.getConstructor(outerClass);
    } catch (NoSuchMethodException e) {
      assert false : "no constructor; message=" + e.getMessage();
    }
    return constructor;
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Clients can check whether newInstance is called on an inner class constructor and whether the first argument is null. If both are true, the client should not perform the call.