byte[] b1 = {1,2,3,4};
byte[] b2 = {5,6,7,8};

ByteArrayOutputStream bos = new ByteArrayOutputStream();
bos.write(b1, 0, b1.length);
bos.write(b2, 0, b2.length); 
byte[] b3 = bos.toByteArray(); //相当于b2接到b1后面，得到一个新的byte数组b3

ByteArrayInputStream bis = new ByteArrayInputStream(b3); 
int n = 0;
while ((n=bis.read()) != -1) { //从字节流中读入字节并输出
    System.out.println(n);
}