CSV processing with Tablesaw

Importing Data in Java

Anthony Markham

VP Quant Developer

Reading CSV files

Read CSV files using read().csv()

import tech.tablesaw.api.Table;

// Read in data
Table dataTable = Table.read().csv("data.csv");

Automatically detects column types, creating a structured Table object 💡

CSV reading options

Use CsvReadOptions for more control

import tech.tablesaw.io.csv.CsvReadOptions;

CsvReadOptions options = CsvReadOptions.builder("data.csv")

            .separator(';')                     // Use semicolon as delimiter

            .header(true)                       // First row contains headers

            .missingValueIndicator("N/A")        // Treat "N/A" as missing data

            .build();


// Load the table using the custom options
Table table = Table.read().csv(options);

Writing CSV files

Use write().csv() for basic CSV export
Imported with Table class
Preserves column types and structure
Handles special characters automatically

// Write dataTable to output.csv
dataTable.write().csv("output.csv");

CSV writing options

Use CsvWriteOptions to specify options for writing

CsvWriteOptions writeOptions = CsvWriteOptions
    .builder("output.csv")

    .header(true)           // Include column headers

    .separator(';')         // Use semicolon delimiter

    .quoteAlways(true)      // Quote all fields

    .lineEnd("\r\n")        // Windows-style line endings

    .build();

// Write the CSV using the custom options
Table.write().csv(writeOptions);

CSV workflow

Complete workflow: read -> inspect -> process -> write
Non-destructive operations (creates new files) 📁

// Read CSV, modify, and write back
Table students = Table.read().csv("students.csv");

// View structure
System.out.println(students.structure());

// Save as new file
students.write().csv("students_processed.csv");

Let's practice!

Importing Data in Java