console

$ javac -XDignore.symbol.file Test.java                                                                                                                                                  
Note: Test.java uses or overrides a deprecated API.                                                                                                                                            
Note: Recompile with -Xlint:deprecation for details.                                                                                                                                                 

$ java Test
Hey y'all 👍@135fbaa4
[public void Hey y'all 👍.call "this" method :)()]

Test.java

import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;

import java.util.Arrays;

public class Test {
  public static void main(String[] args) throws Throwable {
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
    cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, "Hey y'all \uD83D\uDC4D", null, "java/lang/Object", null);
    MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
    mv.visitCode();
    mv.visitVarInsn(Opcodes.ALOAD, 0);
    mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
    mv.visitInsn(Opcodes.RETURN);
    mv.visitMaxs(1, 1);
    mv.visitEnd();

    mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "call \"this\" method :)", "()V", null, null);
    mv.visitCode();
    mv.visitInsn(Opcodes.RETURN);
    mv.visitMaxs(1, 1);
    mv.visitEnd();

    cw.visitEnd();
    byte[] bytes = cw.toByteArray();
    
    new ClassLoader() {{
      Class<?> klass = defineClass(bytes, 0, bytes.length);
      System.out.println(klass.newInstance());
      System.out.println(Arrays.toString(klass.getDeclaredMethods()));
    }};
  }

}