Find File Path and Read the FIle

Question

I know that the file is in Device Storage/WhatsApp/Media/WhatsApp Documents and I want to read it (in fact there are many files there and I want to read any of them).

I am using Intent to get all pdf files.

In onActivityResult... if (resultCode == RESULT_OK) { I am doing:

String FilePath = data.getData().getPath();

                    FilePath = FilePath.substring(FilePath.lastIndexOf('/') + 1).trim();

                    String path = this.getFilesDir().getAbsolutePath();
                    String alternatePath = "Device Storage\\WhatsApp\\Media\\WhatsApp Documents";
                    File file = new File( alternatePath+ "\\" + FilePath);

Next I am doing all the FileInputStream etc stuff. But for some reason, it is giving filenotfound exception.

Please let me know where I am doing wrong.

P.S. the startactivityforresult part:

savebtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
                intent.setType("application/pdf");
                startActivityForResult(intent,PICKFILE_RESULT_CODE); 

            }
        });