@Override public boolean equals(Object obj){
  if (this == obj) {
    return true;
  }
  if (obj == null) {
    return false;
  }
  if (!(obj instanceof ColumnSchema)) {
    return false;
  }
  ColumnSchema other=(ColumnSchema)obj;
  if (columnName == null) {
    if (other.columnName != null) {
      return false;
    }
  }
 else   if (!columnName.equals(other.columnName)) {
    return false;
  }
  return true;
}

@ Override public boolean equals ( Object obj ) { if ( this == obj ) { return true ; } if ( obj == null ) { return false ; } if ( ! ( obj instanceof ColumnSchema ) ) { return false ; } ColumnSchema other = ( ColumnSchema ) obj ; if ( columnName == null ) { if ( other . columnName != null ) { return false ; } } else if ( ! columnName . equals ( other . columnName ) ) { return false ; } return true ; }
overridden equals method for columnschema
