In my Java application I import some CSV files in PostgreSQL 10.3 with PgAdmin4 (JDBC).
private static void importDB(String path, String type) { 
    Statement stmt = null;
    try {
        Class.forName(DRIVER_CLASS_NAME);
            c = DriverManager.getConnection(DB_URL, USER, PASS);
            stmt = c.createStatement();
            //System.out.println(''"+path+"');
            String sql = "COPY "+type+" from '"+path+"' CSV HEADER";
            stmt.executeUpdate(sql);
            stmt.close();
            c.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
}
Now: if I modify some non-key-values in the CSV file and try to re-import there's an obvious primary key problem because it's just like another copy of the same file I imported first. Assuming that tables in PgAdmin4 has primary keys (id,sat), how can I check these keys in the table(in the rows actually) and modify the other non-key data? Just like overwriting them.
