parser = new ExpressionParser("var1", String.class);
parser.createVariable("var1", String.class, "");
try
{
//initial state
strResult = (String)parser.evaluate();
Assert.assertNotNull(strResult);
Assert.assertTrue(strResult.isEmpty());
//set to value (using variable name)
parser.set("var1", "some-string");
strResult = (String)parser.evaluate();