enter code here String templateId = "45deb3ff-6054-4316-bd4d-a3cee82ff527";
    TemplatesApi templateApi = new TemplatesApi();
    EnvelopeTemplate envelopeTemplate;
    try {
        envelopeTemplate = templateApi.get(accountId, templateId);

        List<Document> documentList = envelopeTemplate.getDocuments();

        Document document = documentList.get(0);

        String documentId = document.getDocumentId();

        DocumentFieldsInformation dfi = templateApi.listDocumentFields(accountId, templateId, documentId);
        CustomFields cf= templateApi.listCustomFields(accountId, templateId);
        List<TextCustomField> lcf = cf.getTextCustomFields();

        for(int i = 0; i < lcf.size(); i++) {
            TextCustomField aaa = lcf.get(i);
        }

        List<NameValue> nv = dfi.getDocumentFields();
        Iterator<NameValue> i = nv.iterator();
        while(i.hasNext()) {
            NameValue nv2 = i.next();
            String name = nv2.getName();
            String value = nv2.getValue();
            nv2.setValue("test");
        }
    } catch (ApiException e) {
    }