Java SimpleScriptContext set attribute with different isolation levels

import javax.script.Bindings;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleScriptContext;

public class Main {
  public static void main(String[] args) throws ScriptException {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");

    manager.put("n1", 100);

    String script = "var sum = n1 + n2;" + // 
                    "print(msg + " + "' n1=' + n1 + ', n2=' + n2 + " + "', sum=' + sum);";

    engine.put("n2", 200);
    engine.put("msg", "Using the default context:");
    engine.eval(script);/*w  w w .  ja  v a  2s.  c o  m*/

    Bindings bindings = engine.createBindings();
    bindings.put("n2", 300);
    bindings.put("msg", "Using a Bindings:");
    engine.eval(script, bindings);


    ScriptContext ctx = new SimpleScriptContext();
    Bindings ctxGlobalBindings = engine.createBindings();

    ctx.setBindings(ctxGlobalBindings, SimpleScriptContext.GLOBAL_SCOPE);
    ctx.setAttribute("n1", 400, SimpleScriptContext.GLOBAL_SCOPE);
    ctx.setAttribute("n2", 500, SimpleScriptContext.ENGINE_SCOPE);
    ctx.setAttribute("msg", "Using a ScriptContext:", SimpleScriptContext.ENGINE_SCOPE);
    
    engine.eval(script, ctx);

    engine.eval(script);
  }
}