public void setType(EvictionType type) {
      if (this.type != null && this.type != type) {
        throw new IllegalArgumentException("Type conflict. Type is already set to " + this.type);
      }
      this.type = type;
    }
once a type is set, it can not be changed to another value.

@param type eviction type
@throws IllegalArgumentException if type is already set to another value. this is to
        prevent users from trying to send in conflicting attributes in json
        format such as {entryCount:10,type:HEAP_PERCENTAGE}
geode-management/src/main/java/org/apache/geode/management/configuration/Region.java