java文件删除不了File类的delete方法删不掉文件的原因以及分析

File directory = null;
            String path = tempPath  + File.separator + fileName;
            directory = new File(path);
            if(!directory.exists()){
                directory.mkdirs();
            }
            Writer out = null;
            FileOutputStream fos = null;
            //这个地方对流的编码不可或缺，使用main（）单独调用时，应该可以，但是如果是web请求导出时导出后word文档就会打不开，并且包XML文件错误。主要是编码格式不正确，无法解析。
            //out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(outFile)));
            for (int i = 0; i < dataMapList.size(); i++) {
                File outFile = new File(path+File.separator+fileName+System.currentTimeMillis() + ".doc");
                if (!outFile.exists()) {
                    outFile.createNewFile();
                }
                fos = new FileOutputStream(outFile);
                OutputStreamWriter oWriter = new OutputStreamWriter(fos, "UTF-8");
                out = new BufferedWriter(oWriter);
                t.process(dataMapList.get(i), out);
              
            }
                  out.close();
                fos.close();

while (file.exists()) {
    System.gc();
    file.delete();
}