查看并学习使用StreamResult类的javadoc（ http://java.sun.com/javase/6/docs/api/ ）。
StreamResult的一个构造函数将Writer对象作为参数。你会看到Writer的一个子类是StringWriter。所以要从写入StreamResult的字符串中获取一个字符串，可以构造一个StringWriter，将它放入StreamResult，将Source转换为StreamResult，并从StringWriter获取字符串。

  //为输出创建一个StringWriter 
 StringWriter outWriter = new StringWriter（）; 
 StreamResult result = new StreamResult（outWriter）; 
 ... 
 transformer.transform（source，result）; 
 StringBuffer sb = outWriter.getBuffer（）; 
 String finalstring = sb.toString（）; 
 

I want to convert the stream result output to string since I want to use it in Junit I think that I need to use the string writer but Im not sure how exactly to use it.

StreamResult result = new StreamResult(new File("C:\\file.xml"));
transformer.transform(source, result);

Thanks Fedor

Have a look at and learn to use the javadocs of the StreamResult class (http://java.sun.com/javase/6/docs/api/). One of the constructors of StreamResult takes a Writer object as a parameter. You will see that one of the sub-classes of Writer is StringWriter. So to obtain a string from what is written to the StreamResult, you can construct a StringWriter, put it into the StreamResult, transform() the Source to the StreamResult and get the string from the StringWriter.

//create a StringWriter for the output
StringWriter outWriter = new StringWriter();
StreamResult result = new StreamResult( outWriter );
...
transformer.transform( source, result );  
StringBuffer sb = outWriter.getBuffer(); 
String finalstring = sb.toString();