android - Nullpointer returns when trying to create a file -

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i have code save float array file future use. when call order savearray("the x",x); x float array want save, returns null file , not created.

public void savearray(string filename, float[] array) {          try {             fileoutputstream fos = new fileoutputstream(filename);             objectoutputstream out = new objectoutputstream(fos);             out.writeobject(array);              out.flush();             out.close();          }          catch (ioexception e) {              system.out.println(e);           }       }       public float[] loadarray(string filename) {           try {             fileinputstream fis = new fileinputstream(filename);             objectinputstream in = new objectinputstream(fis);             float[] saved_array = (float[])in.readobject();             in.close();             return saved_array;           }           catch (exception e) {               system.out.println(e);           }           return null;       }

this return me when try save

05-04 07:21:59.547: i/system.out(622): java.io.filenotfoundexception: /the x: open failed: erofs (read-only file system) 05-04 07:21:59.547: i/system.out(622): java.io.filenotfoundexception: /the x: open failed: enoent (no such file or directory) 05-04 07:21:59.557: i/system.out(622): null

edit2: found solution, want more help!

i left savearray before, , create dir , file earlier.

final file dir = new file(context.getfilesdir() + "/works"); dir.mkdirs();  final file file = new file(dir, "the_x.txt"); savearray(file.getpath()+file.getname(),x);

and seems saved. now, try load on array, new array "a" never change values. think mistake? above loadarray function. try these:

a = loadarray(file.getpath()+file.getname()); = loadarray(file.getname()); = loadarray(file.getpath()); = loadarray("the_x.txt");

if writting file in sd card need following permissions 

<uses-permission android:name="android.permission.receive_boot_completed" > </uses-permission> <uses-permission android:name="android.permission.write_external_storage" > </uses-permission>

hence filanem should soething "/sdcard/yourfile.txt"

you can use thing

use 

        objectoutputstream objectoutputstream = new objectoutputstream(                 context.openfileoutput(                         filename, context.mode_private));

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