Java uses IO stream to copy photos complete examples and detailed analysis

Import Java.io.FileInputStream;
Import Java.io.FileOutputStream;
/**

* Precautions:
* int Java.io.FileInputStream.read (byte[] b) throws IOException
* Official document Description of the method:
* Reads up to b.length bytes of the data from this input stream into an array of bytes.
* This method blocks until some input is available.
* That can be understood:
* FileInputStream will continuously read byte data into byte array B.
* Just read it once, then we perform a write operation accordingly:
* Fileoutputstream.write (Temp,0,len);
* What happens when this reading process terminates?
* When the end of the data has been read, there is an identifier-1; the expression has reached the end.
*
* A less appropriate understanding:
* FileInputStream will read byte data into byte array B again and again.
* After each reading, a little pause is performed, and then the
* Fileoutputstream.write (Temp,0,len);
* Perform data write operations.
*
* In fact, the following understanding is more appropriate:
* FileInputStream is constantly reading the data (rather than imagining it to be read again and again with a paused nature).
* But it must not exceed the size of b.length every time it is read, but it may not be the same length,
* For example: In most cases, the last time the number of bytes read will be less than the b.length size.
* Every time the Read () method is read, the data is stored in byte array B, and the method
* Also returns the number of bytes read (len).
* So we write to the data from O to Len in byte array B:
* Fileoutputstream.write (Temp,0,len);
*
* Now it's clear why use:
* Fileoutputstream.write (temp);
* is inaccurate and is likely to cause the copied photo to be larger than the original photo.
* Because Fileoutputstream.write (temp); method is always
* Write the size of the B-byte array, not how many are actually in B
Data.
* Such operations in the first few times there is no problem, because each loaded
* are all data of B-byte array size, but the last one is often loaded with dissatisfaction
* B. So each time it should be based on the actual data in B exactly how much to do
* operation is the use of fileoutputstream.write (Temp,0,len);
* can take into account every time.
*/
public class Copyphoto {
public static void Main (string[] args) {
Copyphoto Copyphoto = new Copyphoto ();
Copyphoto.copy ();
}

private void Copy () {
try {
FileInputStream fileinputstream=new FileInputStream ("d:\\c.jpg");
FileOutputStream fileoutputstream=new FileOutputStream ("d:\\new.jpg");
int len=0;
byte temp []=new byte[1024*8];;
while ((Len=fileinputstream.read (temp))!=-1) {
System.out.println ("len=" +len);
It's Right
Fileoutputstream.write (Temp,0,len);
It is wrong
Fileoutputstream.write (temp);
}
Fileoutputstream.close ();
Fileinputstream.close ();
} catch (Exception e) {
}

}

}

Java uses IO stream to copy photos complete examples and detailed analysis