code: public static void setGlobalVar(String key, String value) {
  		validateKey(key);
  
  		if (value == null) {
  			globalVars.remove(key);
  		} else {
  			validateValueLength(value);
  			if (globalVars.size() > MAX_GLOBAL_VARS) {
  				throw new IllegalArgumentException("Maximum number of global variables reached: " + MAX_GLOBAL_VARS);
  			}
  			globalVars.put(key, value);
  		}
  	}
docs: Sets or removes a global variable.
  <p>
  The variable is removed when the {@code value} is {@code null}.
  
  @param key the key of the variable.
  @param value the value of the variable.
  @throws IllegalArgumentException if one of the following conditions is met:
  <ul>
  <li>The {@code key} is {@code null} or its length is higher than the maximum allowed
  ({@value #MAX_KEY_SIZE});</li>
  <li>The {@code value}'s length is higher than the maximum allowed ({@value #MAX_VALUE_SIZE});</li>
  <li>The number of global variables is higher than the maximum allowed ({@value #MAX_GLOBAL_VARS});</li>
  </ul>