How to declare foreign keys in Apache Derby?

I am trying to make a R.D.B. at the moment, but I can't seem to get the foreign keys working. When running the program, the two tables without foreign keys (Words and PDFs) are created and then it has a run-time error at the Index table:

> Table 'INDEX' contains a constraint definition with column 'WORDID' which is not in the table. Derby shut down normally

Here is my code:

new String createSQL3 = "create table Index (" 
        + " IndexID integer not null generated always as"
        + " identity (start with 1, increment by 1),"
        + " IndexPage integer not null, IndexOccurences integer not null,"
        + " constraint IndexID_PK primary key (IndexID),"
        + " constraint WordID_FK FOREIGN KEY (WordID) REFERENCES Words(WordID),"
        + " constraint PDFID_FK FOREIGN KEY (PDFID) REFERENCES PDFs(PDFID))";
            
        statement.execute(createSQL3);
        System.out.println("Table Index created successfully");
         
        connection.commit();
        
    } catch (SQLException EX) {
        System.out.println(EX.getMessage());

This syntax:

constraint WordID_FK FOREIGN KEY (WordID) REFERENCES Words(WordID)

says that you want the column WordID in the table Index to be a reference to the column WordID in the table Words.

But you did not define a column named WordID in the table Index, as the message says. Your Index table has only three columns: IndexID, IndexPage, and IndexOccurrences.

You probably want to have something like

WordID integer,

in your definition of table Index.