reflection-java17.jshell

// Start jshell as such:
// jshell -R--add-opens=java.base/java.lang=ALL-UNNAMED -R--add-opens=java.base/java.lang.reflect=ALL-UNNAMED

var GET_VALUE = String.class.getDeclaredField("value");
GET_VALUE.setAccessible(true);

var name = "Foo Bar";

var bytes = name.getBytes();
var rawBytes = new byte[bytes.length];
System.arraycopy(bytes, 0, rawBytes, 0, 7);
var reflectionBytes = GET_VALUE.get(name);

System.out.println("Are all arrays of the same type?");
System.out.println(bytes.getClass().equals(reflectionBytes.getClass()));
System.out.println(rawBytes.getClass().equals(reflectionBytes.getClass()));
System.out.println(bytes.getClass().equals(rawBytes.getClass()));
System.out.println(reflectionBytes.getClass());

System.out.println("bytes: " + java.util.Arrays.toString(bytes));
System.out.println("rawBytes: " + java.util.Arrays.toString(rawBytes));

bytes[0] = (byte) 'B';
rawBytes[0] = (byte) 'B';
var newString = new String(bytes);
System.out.println("newString: " + newString);
System.out.println("Are both non-reflection arrays content equal? 'bytes' and 'rawBytes': " + java.util.Arrays.equals(bytes, rawBytes));

System.out.println("Now let's play with the reflection-sourced byte array...");
System.out.println("reflectionBytes: " + java.util.Arrays.toString(reflectionBytes)); // here you will see a 'no suitable method found'

reflectionBytes[0] = (byte) 'B';
var newReflectionString = new String(reflectionBytes); // here you will see a 'no suitable constructor found'
System.out.println("Reflection String: " + newReflectionString); // here, of course, symbol not found

/exit

1. Using --add-opens on JDK packages is a bad idea. JDK implementation can and will change. And that's break your code that uses deep reflection.

2. In any case you don't need to open up java.lang.reflect package. You just need to open java.lang (because you only use deep reflection on java.lang.String)

3. In line 12, you have

   var reflectionBytes = GET_VALUE.get(name);

GET_VALUE is a java.lang.reflect.Field instance. "get" method returns java.lang.Object type. So type inferred for reflectionBytes is "Object" and that's why you get subsequent errors.

if you change that to

var reflectionBytes = (byte[])GET_VALUE.get(name);

the above code will run fine.