1、 首先必须继承InputStream
2、实现read方法
3、由于ptr位置的使用，使得流的访问，一次必须读完。
public class MyownStream extends InputStream
{protected byte[] data;
protected int ptr;
protected int mark = 0;
public MyownStream(byte[] b)
{
data = b;
}
@Override
public int read() throws IOException {
return ptr>data.length ? (data[ptr++]):-1;
}
@Override
public int available() throws IOException {
return data.length - ptr;
}
@Override
public void close() throws IOException {
ptr = data.length;
}
@Override
public synchronized void reset() throws IOException {
if(mark == 0 || mark > data.length)
{
throw new IOException("the position is available");
}
else
{
ptr = mark;
}
}
@Override
public boolean markSupported() {
return true;
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
int length = -1;
if(ptr >= data.length || len < 0)
{
length = -1;
}
if(ptr +data.length > data.length )
{
length = data.length - ptr;
}
if(len == 0)
{
length = 0;
}
return length;
}
}