Copying data from one file to another file very slow in android?

Please check the code, what I did is increased the buffer size and flushing the data as soon as it touches 1 MB, so that you don't encounter Out of memory error.

Reason is mainly due to small buffer size which takes time in writing small bytes of information. Better to put a large chunk at a time.

You can modify these values according to your needs.

public void copyData( InputStream in, OutputStream out ) throws IOException { try { int numRead = 0; byte[] buf = new byte[102400]; long total = 0; while ( ( numRead = in.read( buf ) ) >= 0 ) { total += numRead; out.write( buf, 0, numRead ); //flush after 1MB, so as heap memory doesn't fall short if (total > 1024 * 1024) { total = 0; out.flush(); } } out.close(); in.close(); } catch ( java.io.IOException e ) { } } 

I am copying data from one file to another file.

No you aren't. You are decrypting an input stream and writing the plaintext to an output stream.

It takes more time.

More time than what?

What's the reason?

Basically your tiny buffer size. Raise it to at least 8192 bytes: more if there continues to be a benefit.

int numRead = 0; 

You don't need to initialize this variable.

byte[] buf = new byte[512]; 

See above. Change to at least 8192.

while ( ( numRead = in.read( buf ) ) >= 0 ) 

read(byte[]) can only return zero if buf.length is zero, which is a programming error you don't want to loop forever on. Change the condition to > 0.

 catch ( java.io.IOException e ) { } 

Never ignore an exception.

I am using operation as Encrypt/Decrypt a file. So that's the reason i am using the buffer size is 512 bytes.

No it isn't. There's nothing about encryption or decryption that requires a 512-byte buffer.

2 Reasons

1. Buffer is too small, make it 4kb or 8kb, keep increasing until your phone crash's, then move 1 step back
2. Reading and Writing need to be on 2 different threads. As reads complete, put it on a q, and as write completes read it from the q. Dont forget to synchronize the q object.

When writing such code, you need to use CPU and Memory to its highest extent. On thread and a while loop is so College C'ish.. :)