Detailed explanation of Android read and write file tool class

public class Utils {
  private static String path1 = ().getAbsolutePath();
  private static String path2 = ().getAbsolutePath();
  private static String pathExt = "/111/222/333/444/555/";
  private static String fileName = "";
 
  public static void write(String str) {
    String filePath = null;
    boolean hasSDCard =().equals(Environment.MEDIA_MOUNTED);
    if (hasSDCard) {
      filePath = path1 + pathExt + fileName;
    } else {
      filePath = path2 + pathExt + fileName;
    }
    try {
      File file = new File(filePath);
      if (!()) {
        //mkdirs() method generates multi-layer folder        //mkdir() method generates layers of folders//        File dir = new File(());
//        ();
        ().mkdirs();//Create the folder outside the file        ();// Generate file      }
      FileOutputStream os = new FileOutputStream(file);
      (());
      ();
    } catch (Exception e) {
      ();
    }
  }
 
  public static String read() {
    String content = "";
    String filePath;
 
    boolean sdcard = ().equals(Environment.MEDIA_MOUNTED);
    if (sdcard) {
      filePath = path1 + pathExt + fileName;
    } else {
      filePath = path2 + pathExt + fileName;
    }
    try {
      File file = new File(filePath);
      if (()) {
        FileInputStream is = new FileInputStream(file);
        InputStreamReader inputReader = new InputStreamReader(is);//Set stream reading method        BufferedReader buffReader = new BufferedReader(inputReader);
        String line;
        try {
          while (null != (line = ())) {
            content += line + "\n";//Read file content          }
          ();//Close the input stream        } catch (IOException e) {
          ();
        } finally {
          try {
            if (null != is) {
              ();
            }
          } catch (IOException e) {
            ();
          }
        }
      }
    } catch (FileNotFoundException e) {
      ();
    }
    return content;
  }
}

<uses-permission android:name=".WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name=".READ_EXTERNAL_STORAGE" />

ArrayList<String> permissionList = new ArrayList<>();
private String[] permissions = {
 ".READ_EXTERNAL_STORAGE",
 ".WRITE_EXTERNAL_STORAGE" };
//Check whether there is permission to write//Judge the mobile version. If it is lower than 6.0, you do not need to apply for permission and take photos directlyif (.SDK_INT >= Build.VERSION_CODES.M) {
 if (checkSelfPermission(permissions[0]) != PackageManager.PERMISSION_GRANTED) {
 (permissions[0]);
 }
 if (checkSelfPermission(permissions[1]) != PackageManager.PERMISSION_GRANTED) {
 (permissions[1]);
 }
 
 if (!()) {
 String[] permissions1 = (new String[()]);
 requestPermissions(permissions1, 1);
 } else {
 ("balabala");
 ();
 }
} else {
 ("balabala");
 ();
}
 
 
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
 switch (requestCode){
 case 1:
  if (PackageManager.PERMISSION_GRANTED == grantResults[0]){
  ("balabala");
  ();
  } else {
  (TAG, "fail: ");
  }
  break;
 }
}