title: Concurrent Modification exception when only values of Hashmap are modified
body: <p>I have code like below, in which the inner loop modifies the Hashmap, but only in a way that no new keys are added or deleted, but only the values are updated. Does this qualifies as modification of a Hashmap, for Concurrent Modification Exception to be thrown ? In current tests that I have done, I haven't found any exception to be thrown though.</p>
  
  <pre><code>for(String variable:variableMap.descendingKeySet()) {
          for (String innerVariable : variableMap.keySet()) {
              variableMap.put(innerVariable, variableMap.get(innerVariable).replace("$" + variable, variableMap.get(variable)));
          }
      }
  </code></pre>