Using the package exp4j always returns UnknownFunctionExpression and UnparsableExpressionException
<p>I have to parse a string which contains a formula for my java project and I wanted to use the package exp4j (http://www.objecthunter.net/exp4j/index.html) to do so. But I always get the same error. Its probably really stupid, but sadly I'm missing it. So here is, what I tried:</p>

<p>I simply tried this for testing:</p>

<pre><code>import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.ExpressionBuilder;

public class Tester {
  public static void main (String[] args){
    Calculable calc = new ExpressionBuilder("3+2").build();
  }
}
</code></pre>

<p>Now eclipse tells me Unhandled exception type UnknownFunctionExpression and Unhandled exception type UnparsableExpressionException.</p>

<p>After that I tried just using one of the examples on the mentioned website:</p>

<pre><code>import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.ExpressionBuilder;

public class Tester {
  public static void main (String[] args){
    double varX = 2;
    double varY = 3;

    Calculable calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
      .withVariable("x", varX)
      .withVariable("y", varY)
      .build();
    double result1=calc.calculate();
  }
}
</code></pre>

<p>resulting in the same exceptions as above.</p>

<p>Sorry for any bad english, I'm german  and thanks for any help :)</p>
