Question: How can I determine if a variable exists from within the Groovy code running in the Scripting Engine?

The variable was put by [ScriptEngine's put method](https://docs.oracle.com/javase/8/docs/api/javax/script/ScriptEngine.html#put(java.lang.String,%20java.lang.Object))

Answer: 
Variables injected by the Scripting Engine are held within
`binding.variables`, so you can e.g. check for variable named `xx`:

```
if (binding.variables["xx"]) ...

```
You can check if the variable is exists by using 'contains' List method:

```
if (list.contains(var)) {
// your code
}

```