java写入错误 java无法写入文件

我的解决方案是使用环境变量来获取存储应用程序数据的正确目录。这是我创建的方法：

private String getAppDataDirectory(String subDirectory, boolean create) {
String appDataDirectory;
try {
appDataDirectory = System.getenv("APPDATA"); //Windows
//todo - could try "ALLUSERSPROFILE"
if (appDataDirectory != null) {
appDataDirectory += File.separator + subDirectory + File.separator;
}
else { //appDataDirectory is null
appDataDirectory = System.getenv("HOME"); //Unix
if (appDataDirectory != null) {
appDataDirectory += File.separator + subDirectory + File.separator;
}
else { //appDataDirectory is still null
throw new Exception("Could not access APPDATA or HOME environment variables");
}
}
}
catch(Exception e) {
e.printStackTrace();
appDataDirectory = "";
}
if (create && appDataDirectory != null && appDataDirectory.length() > 0) {
try {
File dir = new File(appDataDirectory);
dir.mkdir();
}
catch(Exception e) {
e.printStackTrace();
}
}
//log("appDataDirectory: " + appDataDirectory);
return appDataDirectory;
}