A class is accessable from another?

[陈雨亭]

Hello, everyone. I created a class M1450648087 using soot, while the class 
is
executable on some JVMs but not on HotSpot releases:
(1) When the class is tested on IBM's J9 or GIJ, it is executable (i.e., 
"Executed!"
is printed out);
(2) When the class is tested using OpenJDK for Java7/8, it says
"java.lang.IllegalAccessError: tried to access class 
java.lang.AbstractStringBuilder
from class M1450648087"  (the run() method throws 
java.lang.AbstractStringBuilder );
(3) When the class is tested using OpenJDK for Java9, it says 
"java.lang.VerifyError:
Bad type on operand stack ...Type 
'sun/java2d/loops/GraphicsPrimitive$TraceReporter'
(current frame, stack[1]) is not assignable to 'java/lang/Thread' ".
(caused by run()...17: invokevirtual #10                 // Method 
java/lang/Runtime.addShutdownHook:(Ljava/lang/Thread;)V)

My problem is:
(1) Where can I find any reference about whether one class is accessable
from another? Why is the class java.lang.AbstractStringBuilder accessable 
from
M1450648087 when running on J9 but not accessable
when on HotSpot releases?

(2) When can one class be assignable to another? I cannot find any
materials about this. I guess HotSpot for Java9 rejects the assignment
by taking some new rules. Where can I find these rules?

Yuting
*************************************************************************************************************
The decompiled code is given as follows.

javap -verbose M1450648087.class
class M1450648087
  minor version: 0
  major version: 51
  flags: ACC_SUPER
Constant pool:
   #1 = Utf8               Executed!
   #2 = Utf8               ()V
   #3 = Utf8               main
   #4 = String             #1             // Executed!
   #5 = Utf8               java/lang/Object
   #6 = Utf8               java/lang/AbstractStringBuilder
   #7 = Class              #5             // java/lang/Object
   #8 = Methodref          #24.#35        // 
java/io/PrintStream.println:(Ljava/lang/String;)V
   #9 = Utf8               ()Ljava/lang/Runtime;
  #10 = Methodref          #45.#11        // 
java/lang/Runtime.addShutdownHook:(Ljava/lang/Thread;)V
  #11 = NameAndType        #47:#26        // 
addShutdownHook:(Ljava/lang/Thread;)V
  #12 = Utf8               java/lang/System
  #13 = Class              #6             // java/lang/AbstractStringBuilder
  #14 = Class              #12            // java/lang/System
  #15 = Utf8               ()Ljava/lang/Object;
  #16 = Utf8               M1450648087
  #17 = Utf8               sun/java2d/loops/GraphicsPrimitive$TraceReporter
  #18 = Methodref          #41.#29        // 
sun/java2d/loops/GraphicsPrimitive$TraceReporter.setContextClassLoader:(Ljava/lang/ClassLoader;)V
  #19 = Utf8               run
  #20 = Methodref          #41.#23        // 
sun/java2d/loops/GraphicsPrimitive$TraceReporter."<init>":()V
  #21 = Utf8               ([Ljava/lang/String;)V
  #22 = Class              #16            // M1450648087
  #23 = NameAndType        #30:#2         // "<init>":()V
  #24 = Class              #44            // java/io/PrintStream
  #25 = Utf8               Exceptions
  #26 = Utf8               (Ljava/lang/Thread;)V
  #27 = Utf8               SourceFile
  #28 = Utf8               println
  #29 = NameAndType        #48:#49        // 
setContextClassLoader:(Ljava/lang/ClassLoader;)V
  #30 = Utf8               <init>
  #31 = NameAndType        #32:#46        // out:Ljava/io/PrintStream;
  #32 = Utf8               out
  #33 = NameAndType        #38:#9         // 
getRuntime:()Ljava/lang/Runtime;
  #34 = Methodref          #7.#23         // java/lang/Object."<init>":()V
  #35 = NameAndType        #28:#42        // println:(Ljava/lang/String;)V
  #36 = Methodref          #45.#33        // 
java/lang/Runtime.getRuntime:()Ljava/lang/Runtime;
  #37 = Utf8               Jasmin
  #38 = Utf8               getRuntime
  #39 = Utf8               java/lang/Runtime
  #40 = Fieldref           #14.#31        // 
java/lang/System.out:Ljava/io/PrintStream;
  #41 = Class              #17            // 
sun/java2d/loops/GraphicsPrimitive$TraceReporter
  #42 = Utf8               (Ljava/lang/String;)V
  #43 = Utf8               Code
  #44 = Utf8               java/io/PrintStream
  #45 = Class              #39            // java/lang/Runtime
  #46 = Utf8               Ljava/io/PrintStream;
  #47 = Utf8               addShutdownHook
  #48 = Utf8               setContextClassLoader
  #49 = Utf8               (Ljava/lang/ClassLoader;)V
{
  M1450648087();
    descriptor: ()V
    flags:
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #34                 // Method 
java/lang/Object."<init>":()V
         4: return

  public java.lang.Object run() throws java.lang.AbstractStringBuilder;
    descriptor: ()Ljava/lang/Object;
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: new           #41                 // class 
sun/java2d/loops/GraphicsPrimitive$TraceReporter
         3: dup
         4: invokespecial #20                 // Method 
sun/java2d/loops/GraphicsPrimitive$TraceReporter."<init>":()V
         7: astore_0
         8: aload_0
         9: aconst_null
        10: invokevirtual #18                 // Method 
sun/java2d/loops/GraphicsPrimitive$TraceReporter.setContextClassLoader:(Ljava/lang/ClassLoader;)V
        13: invokestatic  #36                 // Method 
java/lang/Runtime.getRuntime:()Ljava/lang/Runtime;
        16: aload_0
        17: invokevirtual #10                 // Method 
java/lang/Runtime.addShutdownHook:(Ljava/lang/Thread;)V
        20: aconst_null
        21: areturn
    Exceptions:
      throws java.lang.AbstractStringBuilder

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     #40                 // Field 
java/lang/System.out:Ljava/io/PrintStream;
         3: ldc           #4                  // String Executed!
         5: invokevirtual #8                  // Method 
java/io/PrintStream.println:(Ljava/lang/String;)V
         8: return
}