Optical Character Recognition (OCR) has become an indispensable technology in modern software development, enabling computers to convert different types of documents, such as images or scanned documents, into editable and searchable text. In the Java ecosystem, integrating OCR capabilities enables powerful document processing, data extraction, and accessibility features. This guide explores how to implement OCR in Java using the Spire.OCR for Java library, leveraging its advanced features to extract text from images with or without positional coordinates.

Table of Contents:

• Why Perform OCR in Java?
• Environment Setup & Configuration
• Extract Text from an Image in Java
• Extract Text with Coordinates from an Image in Java
• Advanced OCR Techniques
  • 1. Enable Auto-Rotation of Images
  • 2. Preserve the Original Layout
• FAQs (Supported Languages and Image Formats)
• Conclusion & Free License

Why Perform OCR in Java?

OCR technology transforms images into machine-readable text. Java developers leverage OCR for:

• Automating invoice/receipt processing
• Digitizing printed records and forms
• Enabling text search in scanned documents
• Extracting structured data with spatial coordinates

Spire.OCR for Java stands out with its:

• Advanced OCR algorithms ensure accurate text recognition.
• Support for multiple image formats and languages.
• Batch processing of multiple images, improving efficiency.
• Ease of integration with Java applications

Environment Setup & Configuration

Step 1: Add Spire.OCR to Your Project

Add the following to your pom.xml:

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependency>
    <groupId>e-iceblue</groupId>
    <artifactId>spire.ocr</artifactId>
    <version>2.1.1</version>
</dependency>

Alternatively, you can download the Spire.OCR for Java library, and then add it to your Java project.

Step 2: Download the OCR Model Files

Spire.OCR for Java relies on pre-trained models to extract image text. Download the OCR model files for your OS:

• Windows x64
• Linux x64
• macOS

After downloading, unzip the files to a directory (e.g., F:\win-x64)

Extract Text from an Image in Java

The following is a basic text extraction example, i.e., reading text from an image and saving it to .txt files.

Use Cases:

• Archiving printed materials (e.g., books, newspapers) as digital text.
• Converting images (e.g., screenshots, memes, signs) into shareable/editable text.

Java code to get text from an image:

import com.spire.ocr.*;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class ocrJava {
    public static void main(String[] args) throws Exception {
            // Create an instance of the OcrScanner class
            OcrScanner scanner = new OcrScanner();

            // Create an instance of the ConfigureOptions class
            ConfigureOptions configureOptions = new ConfigureOptions();

            // Set the path to the OCR model
            configureOptions.setModelPath("F:\\win-x64");

            // Set the language for text recognition
            configureOptions.setLanguage("English");

            // Apply the configuration options to the scanner
            scanner.ConfigureDependencies(configureOptions);

            // Extract text from an image
            scanner.scan("sample.png");
            String text = scanner.getText().toString();

            // Save the extracted text to a text file
            try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"))) {
                writer.write(text);
            } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Key Steps:

1. Initialize Scanner: OcrScanner handles OCR operations

2. Configure Settings:

   • setModelPath(): Location of OCR model files
   • setLanguage(): Supports multiple languages (Chinese, Spanish, etc.)

3. Process Image: scan() performs OCR on the image file

4. Export Text: getText() retrieves results as a string

Output:

Extract Text with Coordinates from an Image in Java

In some applications, knowing the position of text within the image is crucial, for example, when processing structured documents like invoices or forms. The Spire.OCR library supports this through its block-based text extraction feature.

Use Cases:

• Automated invoice processing (locate amounts, dates)
• Form data extraction (identify fields by position)

Java code to extract text with coordinates:

import com.spire.ocr.*;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class ExtractWithCoordinates {
    public static void main(String[] args) throws Exception {
            // Create an instance of the OcrScanner class
            OcrScanner scanner = new OcrScanner();

            // Create an instance of the ConfigureOptions class
            ConfigureOptions configureOptions = new ConfigureOptions();

            // Set the path to the OCR model
            configureOptions.setModelPath("F:\\win-x64");

            // Set the language for text recognition
            configureOptions.setLanguage("English");

            // Apply the configuration options to the scanner
            scanner.ConfigureDependencies(configureOptions);

            // Extract text from an image
            scanner.scan("invoice.png");
            IOCRText text = scanner.getText();

            // Create a list to store information
            List<String> results = new ArrayList<>();

            // Iterate through each detected text block
            for (IOCRTextBlock block : text.getBlocks()) {
                // Add the extracted text and coordinates to the list
                results.add("Block Text: " + block.getText());
                results.add("Coordinates: " + block.getBox());
                results.add("---------");
            }

            // Save to a text file
            try {
                Files.write(Paths.get("ExtractWithCoordinates.txt"), results);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

Key Features:

1. Text & Coordinate Extraction:

   • Iterates over text blocks detected in the image.

   • getText(): Returns an IOCRText object containing recognized text.

   • getBox(): Returns bounding box coordinates [x, y, width, height]

2. Efficient File Writing:

   • Uses Java NIO for efficient file operations.

   • Outputs human-readable results for easy parsing.

Output:

Advanced OCR Techniques

1. Enable Auto-Rotation of Images

For accurate processing of skewed or rotated images, enable the SetAutoRotate() method to rotate the image to the correct upright position automatically:

ConfigureOptions configureOptions = new ConfigureOptions();
configureOptions.SetAutoRotate(true);

2. Preserve the Original Layout

If you need to preserve the original visual layout in the image (e.g., table, multi-column layout), initialize the VisualTextAligner class to enhance the formatting of the extracted text.

// Align the recognized text (for better formatting)
VisualTextAligner visualTextAligner = new VisualTextAligner(scanner.getText());
String scannedText = visualTextAligner.toString();

FAQs (Supported Languages and Image Formats)

Q1: What image formats does Spire.OCR for Java support?

A: Spire.OCR for Java supports all common formats:

• PNG
• JPEG/JPG
• BMP
• TIFF
• GIF

Q2: What languages does Spire.OCR for Java support?

A: Multiple languages are supported:

• English (default)
• Chinese (Simplified and Traditional)
• Japanese
• Korean
• German
• French

Q3: How to improve OCR accuracy?

A: To boost accuracy:

• Use high-quality images (300+ DPI, well-lit, low noise).
• Preprocess images (adjust contrast, remove artifacts) before scanning.
• Specify the correct language(s) for the text in the image.

Q4: Can Spire.OCR for Java extract text from scanned PDFs?

A: This task requires the Spire.PDF for Java integration to convert PDFs to images or extract images from scanned PDFs first, and then use the above Java examples to get text from the images.

Conclusion & Free License

This guide provides a comprehensive roadmap for mastering Spire.OCR for Java, equipping developers with the knowledge to seamlessly integrate powerful OCR capabilities into their Java applications. From step-by-step installation to implementing basic and advanced text extraction, every critical aspect of recognizing text from images has been covered. Whether you're new to OCR or experienced, you now have the tools to convert images to text simply and effectively.

Request a 30-day free trial license here to enjoy unlimited OCR processing in Java.

Converting CSV files to Excel is a common task for Java developers working on data reporting, analytics pipelines, or file transformation tools. While manual CSV parsing is possible, it often leads to bloated code and limited formatting. Using a dedicated Excel library like Spire.XLS for Java simplifies the process and allows full control over layout, styles, templates, and data consolidation.

In this tutorial, we’ll walk through various use cases to convert CSV to Excel using Java — including basic import/export, formatting, injecting CSV into templates, and merging multiple CSVs into a single Excel file.

Quick Navigation

• Set Up Spire.XLS in Your Java Project
• Convert a CSV File to Excel Using Java
• Format Excel Output Using Java
• Merge Multiple CSV Files into One Excel File
• Tips & Troubleshooting
• Frequently Asked Questions

Set Up Spire.XLS in Your Java Project

Before converting CSV to Excel, you’ll need to add Spire.XLS for Java to your project. It supports both .xls and .xlsx formats and provides a clean API for working with Excel files without relying on Microsoft Office.

Install via Maven

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.xls</artifactId>
        <version>16.10.1</version>
    </dependency>
</dependencies>

Add JAR Manually

Download Spire.XLS for Java and add the JAR to your classpath manually. For smaller projects, you can also use the Free Spire.XLS for Java.

Convert a CSV File to Excel Using Java

The simplest use case is to convert a single .csv file into .xlsx or .xls format in Java. Spire.XLS makes this process easy using just two methods: loadFromFile() to read the CSV, and saveToFile() to export it as Excel.

import com.spire.xls.*;

public class CsvToXlsx {
    public static void main(String[] args) {
        Workbook workbook = new Workbook();
        workbook.loadFromFile("data.csv", ",");
        workbook.saveToFile("output.xlsx", ExcelVersion.Version2013);
    }
}

To generate .xls format instead, use ExcelVersion.Version97to2003.

Below is the output Excel file generated after converting the CSV:

You can also specify a custom delimiter or choose the row/column to begin inserting data — useful if your sheet has titles or a fixed layout.

workbook.loadFromFile("data_semicolon.csv", ";", 3, 2);

Format Excel Output Using Java

When you're exporting CSV for reporting or customer-facing documents, it's often necessary to apply styles for better readability and presentation. Spire.XLS allows you to set cell fonts, colors, and number formats using the CellStyle class, automatically adjust column widths to fit content, and more.

Example: Apply Styling and Auto-Fit Columns

import com.spire.xls.*;

public class CsvToXlsx {
    public static void main(String[] args) {
        Workbook workbook = new Workbook();
        workbook.loadFromFile("data.csv", ",");

        Worksheet sheet = workbook.getWorksheets().get(0);

        // Format header row
        CellStyle headerStyle = workbook.getStyles().addStyle("Header");
        headerStyle.getFont().isBold(true);
        headerStyle.setKnownColor(ExcelColors.LightYellow);
        for (int col = 1; col <= sheet.getLastColumn(); col++) {
            sheet.getCellRange(1, col).setStyle(headerStyle);
        }

        // Format numeric column
        CellStyle numStyle = workbook.getStyles().addStyle("Numbers");
        numStyle.setNumberFormat("#,##0.00");
        sheet.getCellRange("B2:B100").setStyle(numStyle);

        // Auto-fit all columns
        for (int i = 1; i <= sheet.getLastRow(); i++) {
            sheet.autoFitColumn(i);
        }

        workbook.saveToFile("formatted_output.xlsx", ExcelVersion.Version2013);
    }
}

Here’s what the styled Excel output looks like with formatted headers and numeric columns:

Need to use a pre-designed Excel template? You can load an existing .xlsx file and insert your data using methods like insertArray(). Just note that formatting won’t automatically apply — use CellStyle to style your data programmatically.

Merge Multiple CSV Files into One Excel File

When handling batch processing or multi-source datasets, it’s common to combine multiple CSV files into a single Excel workbook. Spire.XLS lets you:

• Merge each CSV into a separate worksheet, or
• Append all CSV content into a single worksheet

Option 1: Separate Worksheets per CSV

import com.spire.xls.*;
import java.io.File;

public class CsvToXlsx {
    public static void main(String[] args) {
        // Get the CSV file names
        File[] csvFiles = new File("CSVs/").listFiles((dir, name) -> name.endsWith(".csv"));
        // Create a workbook and clear all worksheets
        Workbook workbook = new Workbook();
        workbook.getWorksheets().clear();

        for (File csv : csvFiles) {
            // Load the CSV file
            Workbook temp = new Workbook();
            temp.loadFromFile(csv.getAbsolutePath(), ",");
            // Append the CSV file to the workbook as a worksheet
            workbook.getWorksheets().addCopy(temp.getWorksheets().get(0));
        }

        // Save the workbook
        workbook.saveToFile("merged.xlsx", ExcelVersion.Version2016);
    }
}

Each CSV file is placed into its own worksheet in the final Excel file:

Option 2: All Data in a Single Worksheet

import com.spire.xls.*;
import java.io.File;

public class CsvToXlsx {
    public static void main(String[] args) {
        // Get the CSV file names
        File[] csvFiles = new File("CSVs/").listFiles((dir, name) -> name.endsWith(".csv"));
        // Create a workbook
        Workbook workbook = new Workbook();
        // Clear default sheets and add a new one
        workbook.getWorksheets().clear();
        Worksheet sheet = workbook.getWorksheets().add("Sample");

        int startRow = 1;
        boolean isFirstFile = true;

        for (File csv : csvFiles) {
            // Load the CSV data
            Workbook temp = new Workbook();
            temp.loadFromFile(csv.getAbsolutePath(), ",");
            Worksheet tempSheet = temp.getWorksheets().get(0);

            // Check if it's the first file
            int startReadRow = isFirstFile ? 1 : 2;
            isFirstFile = false;

            // Copy the CSV data to the sheet
            for (int r = startReadRow; r <= tempSheet.getLastRow(); r++) {
                for (int c = 1; c <= tempSheet.getLastColumn(); c++) {
                    sheet.getCellRange(startRow, c).setValue(tempSheet.getCellRange(r, c).getText());
                }
                startRow++;
            }
        }

        // Save the merged workbook
        workbook.saveToFile("merged_single_sheet.xlsx", ExcelVersion.Version2016);
    }
}

Below is the final Excel sheet with all CSV data merged into a single worksheet:

Related Article: How to Merge Excel Files Using Java

Tips & Troubleshooting

Problems with your output? Try these fixes:

• Text garbled in Excel → Make sure your CSV is UTF-8 encoded.

• Wrong column alignment? → Check if delimiters are mismatched.

• Large CSV files? → Split files or use multiple sheets for better memory handling.

• Appending files with different structures? → Normalize column headers beforehand.

Conclusion

Whether you're handling a simple CSV file or building a more advanced reporting workflow, Spire.XLS for Java offers a powerful and flexible solution for converting CSV to Excel through Java code. It allows you to convert CSV files to XLSX or XLS with just a few lines of code, apply professional formatting to ensure readability, inject data into pre-designed templates for consistent branding, and even merge multiple CSVs into a single, well-organized workbook. By automating these processes, you can minimize manual effort and generate clean, professional Excel files more efficiently.

You can apply for a free temporary license to experience the full capabilities without limitations.

Frequently Asked Questions

How do I convert CSV to XLSX in Java?

Use Workbook.loadFromFile("file.csv", ",") and then saveToFile("output.xlsx", ExcelVersion.Version2016).

Can I format the Excel output?

Yes. Use CellStyle to control fonts, colors, alignment, and number formats.

Is it possible to use Excel templates for CSV data?

Absolutely. Load a .xlsx template and inject CSV using setText() or insertDataTable().

How can I merge several CSV files into one Excel file?

Use either multiple worksheets or merge everything into one sheet row by row.

Inserting subscript in Excel is a common requirement, especially when dealing with chemical formulas like CO₂, statistical footnotes, or scientific data. Using subscripts helps make data clearer and more polished, enhancing the professionalism of your documents. However, Excel’s built-in subscript feature is cumbersome and doesn’t support batch application, which can significantly slow down your workflow.

Fortunately, with the help of Java code, you can efficiently insert subscripts in Excel, freeing yourself from tedious manual work and making your tasks faster and more professional.

• Preparation
• Insert New Text with Subscript
• Apply Subscript to Existing Text
• Insert Subscript for Multiple Matches in Single Cell
• Conclusion

Preparation

Inserting a subscript in Excel using Java involves adding Java libraries. In today’s blog, we will use Spire.XLS for Java as an example to accomplish this task. Spire.XLS is a powerful Java component that works independently without relying on Microsoft Office. In addition to reading, editing, and converting Excel files, it allows users to perform advanced tasks as well.

To install it on your device, there are two options:

1. If you are using Maven, add the following code to your pom.xml file:

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.xls</artifactId>
        <version>16.10.1</version>
    </dependency>
</dependencies>

1. If you prefer manual installation, download the Spire.XLS package and add the .jar file to your Java IDE.

Inserting Subscript in Excel: How to Insert New Text with Subscript

First, let’s see how to insert new text into an Excel cell with subscript formatting already applied. By setting the subscript when creating a new document, you can generate the final file directly without needing to reopen and adjust it later.

Steps—Inserting subscript in Excel when adding new text with Java:

• Create a Workbook and get a worksheet.
• Get a cell range using Worksheet.getCellRange() method.
• Specify text through CellRange.getRichText().setText() method.
• Create a font through Workbook.createFont() method.
• Set ExcelFont.isSubscript() to true.
• Apply the font to a text range in the cell using RichText.setFont(startIndex, endIndex, font) method.

The following code shows how to insert the text "R100-0.06" into cell B2 and set the subscript:

import com.spire.xls.*;  
  
import java.awt.*;  
  
public class InsertSubscriptNewText {  
  
    public static void main(String[] args) {  
  
        // Create a Workbook instance  
        Workbook workbook = new Workbook();  
  
        // Get the first worksheet  
        Worksheet sheet = workbook.getWorksheets().get(0);  
  
        // Insert text to B2  
        sheet.getCellRange("B2").setText("This is an example of Subscript:");  
  
        // Insert text to B3 and apply subscript effect  
        CellRange range = sheet.getCellRange("B3");  
        range.getRichText().setText("R100-0.06");  
        ExcelFont font = workbook.createFont();  
        font.isSubscript(true);  
        font.setColor(Color.red);  
        range.getRichText().setFont(4, 8, font);  
  
        // Auto fit column width  
        sheet.getAllocatedRange().autoFitColumns();  
  
        // Save the document  
        workbook.saveToFile("/SubscriptNewText.xlsx", ExcelVersion.Version2016);  
    }  
}

Result Preview:

Tip: By setting ExcelFont.isSuperscript() to true, you can apply superscript to text in Excel files.

Inserting Subscript in Excel: Apply Subscript to Existing Text

Although inserting subscripts while creating a new Excel file can simplify later work, in most cases, you’ll need to deal with existing files that already contain content. This section shows you how to quickly apply subscript formatting to existing text in Excel using Java.

Steps—Inserting subscript to Excel file with existing text:

• Create a Workbook instance and read an Excel file.
• Get a worksheet and get the cell range.
• Loop through cells in the cell range and find the text to apply subscript.
• Set the text in the cell’s rich text using RichText.setText() to preserve the existing content.
• Create a font by calling Workbook.createFont() method and configure it as Subscript by setting ExcelFont.isSubscript() to true.
• Apply the subscript using RichText.setFont(index, index, subFont) method.

The following code demonstrates how to set subscripts for chemical formulas in the cells within the A1:A3 range:

import com.spire.xls.*;  
  
public class SubscriptExistingContent {  
  
    public static void main(String[] args) {  
        // Create a Workbook and load an Excel file  
        Workbook workbook = new Workbook();  
        // Load an Excel file  
        workbook.loadFromFile(("/test.xlsx"));  
  
        // Get a worksheet  
        Worksheet sheet = workbook.getWorksheets().get(0);  
  
        // Loop through A1:A3  
        for (int i = 1; i <= 3; i++) {  
            CellRange cell = sheet.getCellRange("A" + i);  
            String text = cell.getText();  
  
            // Find "2" in cells  
            int index = text.indexOf("2");  
            if (index != -1) {  
                // Set RichText to keep original text   
cell.getRichText().setText(text);  
  
                // Create font and set as subscript  
                ExcelFont subFont = workbook.createFont();  
                subFont.isSubscript(true);  
  
                // Apply subscript to "2"  
                cell.getRichText().setFont(index, index, subFont);  
            }  
        }  
  
        // Auto fit columns  
        sheet.getAllocatedRange().autoFitColumns();  
  
        // Save the Excel file  
        workbook.saveToFile("/SubscriptExistingContent.xlsx", ExcelVersion.Version2016);  
    }  
}  

Result Preview:

The above code helps us find and set the first matching character as a subscript in an existing cell. But what if the same character appears multiple times in the same cell? How can we apply subscripts to all of them at once? Let’s explore this in the next section.

Inserting Subscript in Excel: Handle Multiple Matches in a Single Cell

Using a search-and-apply method to set subscript formatting works well when there is only one instance in the cell that needs to be subscripted, such as in H₂. However, if the cell contains a chemical equation, the situation becomes more complex: there might be multiple places where subscripts are needed, along with normal numbers representing coefficients (e.g., 2H₂ + O₂ → 2H₂O). In this case, the solution is to set subscripts precisely by specifying the exact positions of the target characters in the text. Let’s take a look at the detailed steps.

Steps—Inserting multiple subscripts in Excel cells:

• Create a Workbook object and read an Excel file.
• Get a worksheet and a cell range.
• Read text in the cell range and set it to rich text using CellRange.getRichText().setText() method.
• Create a font by calling Workbook.createFont() method and configure it as subscript by setting ExcelFont.isSubscript() to true.
• Apply subscript to specific characters with CellRange.getRichText().setFont(index, index, subFont) method.

The following code demonstrates how to set subscripts for the necessary parts of the chemical equation “2H₂ + O₂ → 2H₂O” in cell C2:

import com.spire.xls.*;  
  
public class SubscriptSpecificCell {  
  
    public static void main(String[] args) {  
        // Create a Workbook instance and load an Excel file  
        Workbook workbook = new Workbook();  
        workbook.loadFromFile(("/test.xlsx"));  
  
        // Get the first worksheet  
        Worksheet sheet = workbook.getWorksheets().get(0);  
  
        // Get a cell range  
        CellRange cell = sheet.getCellRange("C2");  
  
        // Read text from C2  
        String text = cell.getText();  
  
  
        // Set text to RichText  
        cell.getRichText().setText(text);  
  
        // Create font object and set it as subscript  
        ExcelFont subFont = workbook.createFont();  
        subFont.isSubscript(true);  
  
        // Set subscript for specific cell  
        cell.getRichText().setFont(2, 2, subFont);  
        cell.getRichText().setFont(7, 7, subFont);  
        cell.getRichText().setFont(13, 13, subFont);  
  
        // Auto fit columns  
        sheet.getAllocatedRange().autoFitColumns();  
          
        // Save the Excel file  
        workbook.saveToFile("/SubscriptSpecificCell.xlsx", ExcelVersion.Version2016);  
    }  
}

Result Preview:

Conclusion

This guide provides a detailed explanation of how to set subscripts in Excel, whether you need to apply them to a single cell or a range of cells, and whether you’re formatting one instance or multiple occurrences. By the end of this page, inserting subscript in Excel will be a breeze for you. Give Spire.XLS a try and start creating professional Excel workbooks today!