// For complete examples and data files, please go to https://github.com/aspose-words/Aspose.Words-for-Java
// The path to the documents directory.
String dataDir = Utils.getDataDir(ModifyContentControls.class);

// Open the document.
Document doc = new Document(dataDir + "CheckBoxTypeContentControl.docx");

for (Object t : doc.getChildNodes(NodeType.STRUCTURED_DOCUMENT_TAG, true)) {

    StructuredDocumentTag std = (StructuredDocumentTag) t;
    if (std.getSdtType() == SdtType.PLAIN_TEXT) {
        std.removeAllChildren();
        Paragraph para = (Paragraph) std.appendChild(new Paragraph(doc));
        Run run = new Run(doc, "new text goes here");
        para.appendChild(run);
    }
    if (std.getSdtType() == SdtType.DROP_DOWN_LIST) {
        SdtListItem secondItem = std.getListItems().get(2);
        std.getListItems().setSelectedValue(secondItem);
    }
    if (std.getSdtType() == SdtType.PICTURE) {
        Shape shape = (Shape) std.getChild(NodeType.SHAPE, 0, true);
        if (shape.hasImage()) {
            shape.getImageData().setImage(dataDir + "Watermark.png");
        }
    }
    doc.save(dataDir + "output.doc");