Java evaluate a math expression in string

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

public class Test {
  public static void main(String[] args) throws ScriptException {
		ScriptEngineManager mgr = new ScriptEngineManager();
		ScriptEngine engine = mgr.getEngineByName("JavaScript");
		String foo = "2+3";
		System.out.println(engine.eval(foo));
    } 
}