Description Marko Čupić 2021-04-20 03:53:28 EDT

The following:

public class Demo {

	public class Singleton {
		private static Singleton pinstance = new Singleton();
		public static Singleton instance() {
			return pinstance;
		}
		public String message() {
			return "Hello world!";
		}
	}
	
	public static void main(String[] args) {
		System.out.println(Singleton.instance().message());
	}
}

compiles fine in eclipse but JVM chrashes when the program is run:

Exception in thread "main" java.lang.VerifyError: Bad local variable type
Exception Details:
  Location:
    Demo$Singleton.<clinit>()V @4: aload_1
  Reason:
    Type top (current frame, locals[1]) is not assignable to reference type
  Current Frame:
    bci: @4
    flags: { }
    locals: { }
    stack: { uninitialized 0, uninitialized 0 }
  Bytecode:
    0000000: bb00 0159 2bb7 000c b300 10b1          

	at Demo.main(Demo.java:15)

Oracle's compiler (javac) run from command line correctly reports an error:

Demo.java:5: error: non-static variable this cannot be referenced from a static context
		private static Singleton pinstance = new Singleton();

OS is Linux 5.8.0-50-generic #56~20.04.1-Ubuntu SMP Mon Apr 12 21:46:35 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux