@Override
  public boolean contains(Object obj) {
    if (!(obj instanceof Struct)) {
      return false;
    }
    Struct s = (Struct) obj;
    if (!structType.equals(StructTypeImpl.typeFromStruct(s))) {
      return false;
    }
    return containsFieldValues(s.getFieldValues());
  }
Does this set contain specified struct?
geode-core/src/main/java/org/apache/geode/cache/query/internal/StructSet.java