Temperature Conversion with script : ScriptEngines « Development « Java Tutorial

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

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

    String script = "function c2f(degrees){return degrees*9.0/5.0+32;}";
        + "function f2c(degrees){return (degrees-32)*5.0/9.0;}" + " "
        + "function convertTemperature (degrees, toCelsius){"
        + "   if (toCelsius)" + "return f2c (degrees);elsereturn c2f (degrees);}";

    engine.eval(script);
    Invocable invocable = (Invocable) engine;

    TempConversion tc = invocable.getInterface(TempConversion.class);
    if (tc == null)
      System.err.println("Unable to obtain TempConversion interface");
    else {
      System.out.println("212 degrees Fahrenheit = "
          + tc.convertTemperature(212.0, true) + " degrees Celsius");
    }
  }
}

interface TempConversion {
  double convertTemperature(double degrees, boolean toCelsius);
}