You can get FontSetting object for the selected characters, and then change the style. Article Reference from Aspose documentation is http://goo.gl/GhtDDy
EDIT
setValue() method in the API will set the complete value. In your case, you have chunks with associated styles. Ideally, there should be method like appendValue(String, Style), but such method does not exist in the Aspose.Cells library. Please request this feature in Aspose forums.
Check the below method, you can have limited style, only font setting applied in your scenario, with the current API.
I assume that you have an array list of strings (chunks of values) and an array list of styles (associated styles for each chunk). Separator character can be a space.
public static void main(String[] args) throws Exception
{
// Instantiating a Workbook object
Workbook workbook = new Workbook();
// Accessing the added worksheet in the Excel file
Worksheet worksheet = workbook.getWorksheets().get(0);
Cells cells = worksheet.getCells();
ArrayList<String> values = new ArrayList<String>();
ArrayList<Style> styles = new ArrayList<Style>();
// Separator character
String separator = " ";
// I
values.add("I");
styles.add(new Style()); styles.get(0).getFont().setBold(true);
// Want
values.add("Want");
styles.add(new Style()); styles.get(1).getFont().setBold(false);
// Some
values.add("Some");
styles.add(new Style()); styles.get(2).getFont().setBold(true);
// Help
values.add("Help");
styles.add(new Style()); styles.get(3).getFont().setBold(false);
// Get cell A1
Cell cell = cells.get("A1");
appendValuesWithStyles(cell, values, styles, separator);
workbook.save(Common.DATA_DIR + "cellstyle.xlsx");
}
private static void appendValuesWithStyles(Cell cell, ArrayList<String> values, ArrayList<Style> styles, String separator)
{
// Lets combine all chunks, because we can only use setValue()
String allCharacters = "";
// First set the whole value in cell
int iValue = 0;
for (String value : values)
{
allCharacters = allCharacters + value;
if (iValue < values.size())
allCharacters = allCharacters + separator;
iValue++;
}
// Set the value once
cell.setValue(allCharacters);
// Now set the styles
int startIndex = 0, valueLength = 0;
for (int iStyle = 0 ; iStyle < styles.size() ; iStyle++)
{
// Get the associated value and the style.
String value = values.get(iStyle);
Style style = styles.get(iStyle);
// We need the start character and length of string to set the style
valueLength = value.length();
cell.characters(startIndex, valueLength).getFont().setBold(style.getFont().isBold());
// Increment the start index
startIndex = startIndex + valueLength + separator.length();
}
}