Javascript eval in java

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class EvalSample 
{
	public static void main(String[] args) 
	throws Exception
	{
    
    	String expression = "function f(param) { return (param > 10); } f(ext_param_1);";
        
        expression = expression.replace("ext_param_1","12");
        
		ScriptEngine e = new ScriptEngineManager().getEngineByName("js");
		
		Object res = e.eval(expression);

		System.out.println(res); //true
	}
}