我又按照你写的 写了一遍
没有问题 不会报错
import java.io.*;
class CopyImage{
public static void main(String[]args)throws Exception{
FileOutputStream fs = new FileOutputStream("sdjf.jpg");
FileInputStream fis = new FileInputStream("psb.jpg");
int len = 0;
byte [] by = new byte[1];
while((len = fis.read(by))!=-1){
fs.write(by,0,len);
}
fs.close();
fis.close();
}
}
下面我把缓冲区的源码发给你 你自己去理解 我第一的说法有问题
等一下我也还要看一下
private void fill() throws IOException { //这个就是源码中判断缓冲区大小的方法 ，怎么可能没有缓冲区呢
byte[] buffer = getBufIfOpen();
if (markpos < 0)
pos = 0; /* no mark: throw away the buffer */
else if (pos >= buffer.length) /* no room left in buffer */
if (markpos > 0) { /* can throw away early part of the buffer */
int sz = pos - markpos;
System.arraycopy(buffer, markpos, buffer, 0, sz);
pos = sz;
markpos = 0;
} else if (buffer.length >= marklimit) {
markpos = -1; /* buffer got too big, invalidate mark */
pos = 0; /* drop buffer contents */
} else { /* grow buffer */
int nsz = pos * 2;
if (nsz > marklimit)
nsz = marklimit;
byte nbuf[] = new byte[nsz];
System.arraycopy(buffer, 0, nbuf, 0, pos);
if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {
// Can't replace buf if there was an async close.
// Note: This would need to be changed if fill()
// is ever made accessible to multiple threads.
// But for now, the only way CAS can fail is via close.
// assert buf == null;
throw new IOException("Stream closed");
}
buffer = nbuf;
}
count = pos;
int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
if (n > 0)
count = n + pos;
}
/**
* See
* the general contract of the <code>read</code>
* method of <code>InputStream</code>.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* stream is reached.
* @exception IOException if this input stream has been closed by
* invoking its {@link #close()} method,
* or an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public synchronized int read() throws IOException {
if (pos >= count) {
fill();
if (pos >= count)
return -1;
}
return getBufIfOpen()[pos++] & 0xff;
} |
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