Update element of LinkedHashSet which is a collection

Question

I have a nested collection structure representing Schema, Table, Column

public class SSchema{
    private String schemaName;
    private LinkedHashSet<STable> tableSet;
}
public class STable {
    private String tableFullName;
    private String tableDisplayName;
    private LinkedHashSet<SColumn> columnSet;
}
public class SColumn {
    private String columnFullName;
    private String columnDisplayName;
    private String columnType;
}

I retrieve the list of columns from an API and populate a LinkedHashSet of columns, I then get the Tables these columns belong to and am trying to update the LinkedHashSet of Columns inside each Table. Unfortunately, there is no API to get the columns for a table in this API

LinkedHashSet<SColumn> sColumnSet = getSColumnsFromAPI();
LinkedHashSet<STable> sTableSet = getSTablesForColumns(sColumnSet);

In the function getSTablesForColumns,

private LinkedHashSet<STable> getSTablesForColumns(LinkedHashSet<SColumn> sColumnSet) throws IOException,JsonParseException {
        sTableSet = new LinkedHashSet<STable>();
        sColumnSet.forEach(sColumn -> {
        String[] tablesList = getTablesFromApi(sColumn) //get the tables this column is in
        foreach(String tableName:tablesList){
           STable table = STable.builder()
                                  .tableFullName(tableName)
                                  .build();
           //This is where the problem is - need a way to get the existing table
           if(sTableSet.contains(table){
                 // get existing table from sTableSet - how do I do this?
                 existingTable.getColumnSet().add(stiboColumn);
           }
           else { //new table, not in collection
               LinkedHashSet<SColumn> columnSet = new LinkedHashSet<SColumn>();
               columnSet.add(sColumn);
               table.setColumnSet(columnSet);
               sTableSet.add(table);
                 };
            }
      });
    return sTableSet;
}

The question/difficulty I am having is: How do I efficiently find the existing sTable in the LinkedHashSet and update the LinkedHashSet inside this sTable with the additional sColumn?

Edit: I came up with the following fix before the much better solution below:

My earlier solution was to check if the table existed in the collection (I had moved the sTableSet to a class variable):

boolean existingTable=false;
   for(STable sTable : sTableSet){
      String collectionSTableName = sTable.getTableFullName();
      if (collectionSTableName.equals(table)){
            existingTable=true;
            sTable.getColumnSet().add(sColumn);
            break;
      }
   }
   if(existingTable==false) { //new table, not in collection
       LinkedHashSet<SColumn> columnSet = new LinkedHashSet<SColumn>();
       columnSet.add(sColumn);
       table.setColumnSet(columnSet);
       sTableSet.add(table);
   };