<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.doc</artifactId>
        <version>12.4.6</version>
    </dependency>
</dependencies>
    

import com.spire.doc.*;
import com.spire.doc.documents.Paragraph;
import com.spire.doc.documents.ParagraphStyle;


public class SetFont {
    public static void main(String[] args){
        //Create a Document instance
        Document document = new Document();

        //Add a section to this document
        Section section = document.addSection();

        //Add three paragraphs to this section and append text for each of them
        Paragraph para1 = section.addParagraph();
        para1.appendText("Yellowstone National Park");

        Paragraph para2 = section.addParagraph();
        para2.appendText("Yellowstone National Park, or Yellowstone Park for short, is managed by the National Park Service of the United States. On March 1, 1872, it was officially named as a national park to protect wild animals and natural resources, and was included in the World Natural Heritage List in 1978. This is the first national park in the world.");

        Paragraph para3 = section.addParagraph();
        para3.appendText("Yellowstone National Park covers an area of 898317 hectares, mainly located in Wyoming, USA, and partially located in Montana and Idaho. Yellowstone Park is divided into five areas: the Mammoth Hot Spring Area in the northwest is mainly composed of limestone steps, so it is also called hot step area.");

        //Create a ParagraphStyle instance
        ParagraphStyle style1 = new ParagraphStyle(document);

        //Set the first paragraph as the title and set its font
        style1.setName("titleStyle");
        style1.getCharacterFormat().setFontName("Arial");
        style1.getCharacterFormat().setFontSize(16f);
        document.getStyles().add(style1);
        para1.applyStyle("titleStyle");

        //Create a ParagraphStyle instance
        ParagraphStyle style2 = new ParagraphStyle(document);

        //Set the other two paragraphs as the body and set their fonts
        style2.setName("paraStyle");
        style2.getCharacterFormat().setFontName("Times New Roman");
        style2.getCharacterFormat().setFontSize(10f);
        document.getStyles().add(style2);
        para2.applyStyle("paraStyle");
        para3.applyStyle("paraStyle");

        //Save the result docunmen
        document.saveToFile("output/setFont.docx", FileFormat.Docx);
        document.dispose();
    }
}

<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.doc</artifactId>
        <version>12.4.6</version>
    </dependency>
</dependencies>
    

import com.spire.doc.Document;
import com.spire.doc.FileFormat;
import com.spire.doc.Section;
import com.spire.doc.documents.BreakType;
import com.spire.doc.documents.Paragraph;
import com.spire.doc.documents.SubSuperScript;
import com.spire.doc.fields.TextRange;

public class InsertSuperscriptAndSubscript {
    public static void main(String[] args){
        //Create a Document instance
        Document document = new Document();
        //Load a Word document
        document.loadFromFile("Sample.docx");

        //Get the first section
        Section section = document.getSections().get(0);

        //Add a paragraph to the section
        Paragraph paragraph = section.addParagraph();

        //Add normal text to the paragraph
        paragraph.appendText("E = mc");
        //Add superscript text to the paragraph
        TextRange superscriptText = paragraph.appendText("2");
        //Apply superscript formatting to the superscript text
        superscriptText.getCharacterFormat().setSubSuperScript(SubSuperScript.Super_Script);

        //Start a new line
        paragraph.appendBreak(BreakType.Line_Break);

        //Add normal text to the paragraph
        paragraph.appendText("H");
        //Add subscript text to the paragraph
        TextRange subscriptText = paragraph.appendText("2");
        //Apply subscript formatting to the subscript text
        subscriptText.getCharacterFormat().setSubSuperScript(SubSuperScript.Sub_Script);
        //Add normal text to the paragraph
        paragraph.appendText("O");

        //Set font size for the text in the paragraph
        for(Object item : paragraph.getItems())
        {
            if (item instanceof TextRange)
            {
                TextRange textRange = (TextRange)item ;
                textRange.getCharacterFormat().setFontSize(36f);
            }
        }

        //Save the result document
        document.saveToFile("InsertSuperscriptAndSubscript.docx", FileFormat.Docx_2013);
    }
}