You can have a look at the EL (expression language) description here.
Both your code are correct, but I prefer the second one, as comparing a boolean to true or false is redundant.
For better readibility, you can also use the not operator:
<c:if test="${not theBooleanVariable}">It's false!</c:if>
Both works. Instead of == you can write eq
You can check this way too
<c:if test="${theBooleanVariable ne true}">It's false!</c:if>
Source: Stackoverflow.com