File,FileWriter

String src = "测试内容开始"+"\r\n"+
                   "测试结束";	
String fileName = System.getProperty("user.dir")+"/src/com/zjx/proxy/TimeProxy.java";
		File f = new File(fileName);
		FileWriter fw = new FileWriter(f);
		fw.write(src);
		fw.flush();
		if(fw !=null)
			fw.close();