implement via OpenCsvParser

ImportSample2Ctrl.cls

public with sharing class PlanetImportSample2Ctrl {

  public DataImportHistory__c dih { get; set; }

  public PlanetImportSample2Ctrl() {
    System.debug('IN PlanetImportSample2Ctrl');
    dih = new DataImportHistory__c();
  }

  public PageReference createData() {
  
    System.debug('IN createData');
  
    String contents =  dih.ImportData__c;
    
    OpenCSVParser parser = new OpenCSVParser(
      '\t',
      OpenCSVParser.DEFAULT_QUOTE_CHARACTER, 
      OpenCSVParser.DEFAULT_ESCAPE_CHARACTER,
      OpenCSVParser.DEFAULT_STRICT_QUOTES, 
      OpenCSVParser.DEFAULT_IGNORE_LEADING_WHITESPACE
      );
    
    OpenCsvReader reader = new OpenCSVReader(parser, contents, '\n');

    List<List<String>> result = reader.readAll();

    System.debug('result=' + result);
    
    Integer i = 0;
    Integer j = 0;
    
    List<ImportData__c> dataList = new List<ImportData__c>();
    
    for(List<String> resultItems : result) {
      
      j = 0;
      ImportData__c data = new ImportData__c();
      
      for(String resultItem : resultItems) {
        System.debug('i=' + i + '; j=' + j + '; result=' + resultItem);
        
        if( j == 0) {
          data.Data1__c = resultItem;
        } else if( j == 1 ) {
          data.Data2__c = resultItem;
        } else if( j == 2 ) {
          data.Data3__c = resultItem;
        }
        
        j++;
        
      }
      
      dataList.add(data);

      i++;
    }
    
    insert dataList;
    
    dih.ImportData__c = '';
    
    return null;
  
  }
}