how to check if Map is empty or not

i have a res object which has resultMap. i want a code to check if the resultMap is empty if so then display warning message.

<c:if test='${res.resultMap[0] == "null" && res.resultMap == "null"}'><br/>
      <b class="TextWarningText">No Result Found</b>

this does not work
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><c:if test='${res.resultMap[0] == "null" && res.resultMap == "null"}'><br/>  
you could try using  
<c:if test='${empty res.resultMap}'><br/>
But for your way, you should have tried  
<c:if test='${res.resultMap[0] == null && res.resultMap == null}'><br/>
or maybe you want
<c:if test='${res.resultMap[0] == null || res.resultMap == null}'><br/>

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