Java byte[]数组处理工具类以及具体例子

截取byte数组一般会用到的方法

/*
*
*destPos, int length)
src:源数组;
srcPos:源数组要复制的起始位置;
dest:目的数组;
destPos:目的数组放置的起始位置;
length:复制的长度.
*/
public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)

byte转int

public static int bytesToInt(byte[] date, int start) {
        if (date.length < start + 4) {
            return 0;
        }
        return date[start] & 0xFF
                | date[(start + 1)] << 8 & 0xFF00
                | date[(start + 2)] << 16 & 0xFF0000
                | date[(start + 3)] << 24 & 0xFF000000;
    }

byte 转long

public static long bytesToLong(byte[] byteNum, int start) {
        long l2;
        if (byteNum.length < start + 8) {
            l2 = 0L;
            return l2;
        }
        long l1 = 0L;
        int i = start;
        for (; ; ) {
            l2 = l1;
            if (i >= start + 8) {
                break;
            }
            l1 = l1 << 8 | byteNum[i] & 0xFF;
            i += 1;
        }
        return l2;
    }

long转byte数组

public static byte[] longToBytes(long num) {
        byte[] byteNum = new byte[8];
        int i = 0;
        while (i < 8) {
            int offset = 64 - (i + 1) * 8;
            byteNum[i] = ((byte) (int) ((num >> offset) & 0xFF));
            //byteNum[i] = ((byte) (int) (num >> 64 - (i + 1) * 8 & 0xFF));
            i += 1;
        }
        return byteNum;
    }

byte转String

public static String bytesToString(byte[] data, int start, int lenth) {
        if (data == null) {
            return null;
        }
        String str = "";
        try {
            str = new String(data, start, lenth, "utf-8");
            int pos = str.indexOf(0);
            if (pos > 0) {
                str = str.substring(0, str.indexOf(0));
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return str;

    }

打印byte数组到控制台

private static String fromBytes(byte[] buffer, int length) {
        if (null == buffer) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            String tempString = Integer.toHexString(0xFF & buffer[i]);
            if (tempString.length() < 2) {
                sb.append("0");
            }
            sb.append(tempString.toUpperCase());

            if (i != length - 1) {
                sb.append(" ");
            }
        }
        return sb.toString();
    }

    private static String fromBytes(byte[] buffer, int start, int length) {
        if (null == buffer) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            String tempString = Integer.toHexString(0xFF & buffer[start + i]);
            if (tempString.length() < 2) {
                sb.append("0");
            }
            sb.append(tempString.toUpperCase());

            if (i != length - 1) {
                sb.append(" ");
            }
        }
        return sb.toString();
    }

---

使用例子

比如我们一个完整的数据帧的结构是这样的。

字节	内容	说明
0-3	type	数据类型
4-7	sub_type	数据子类型
8-11	sub_type1	数据子类型（保留）
12-15	len	数据长度
16-N	data	数据内容

帧头：A1FF1AFF 帧尾：1AFFA1FF (帧头，帧尾，不包含在数据长度中)

比如要传递音乐的信息。音乐信息media(type = 0x13，subType = 0x03)的帧结构如下：

id	name	byte	meaning
1	index	4	位置
2	type	4	类 型
3	id	4	id
4	title	128	音乐 ID3 title
5	album	128	专辑名
6	artist	128	歌手
7	name	128	文件名

音乐列表ListMedia帧组成(type = 0x03,sybType = 0x02)

id	name	byte	meaning
1	start	4	开始位置
2	count	4	条数
3	media	同media帧组成

具体的Java代码如下：

//media数据帧封装
public class MediaMetaData implements DataBase {
    public static int bytesTotal = 524;
    public int index;
    public int type;
    public int id;
    public String title;
    public String album;
    public String artist;
    public String name;
    public int mSubType = 0x03;
    public int mType = 0x13;

    public void getDataFromBytes(byte[] data) {
        this.index = Utils.bytesToInt(data, 0);
        this.type = Utils.bytesToInt(data, 4);
        this.id = Utils.bytesToInt(data, 8);
        this.title = Utils.bytesToString(data, 12, 128);
        this.album = Utils.bytesToString(data, 140, 128);
        this.artist = Utils.bytesToString(data, 268, 128);
        this.name = Utils.bytesToString(data, 396, 128);
    }

    public byte[] toBytes() {
        byte[] data = new byte[bytesTotal];
        System.arraycopy(Utils.intToBytes(index), 0, data, 0, 4);
        System.arraycopy(Utils.intToBytes(type), 0, data, 4, 4);
        System.arraycopy(Utils.intToBytes(id), 0, data, 8, 4);
        if (title == null) {
            title = "";
        }
        if (album == null) {
            album = "";
        }
        if (artist == null) {
            artist = "";
        }
        if (name == null) {
            name = "";
        }
        byte[] title128 = new byte[128];
        byte[] titleBytes = title.getBytes();
        if (titleBytes.length <= 128) {
            System.arraycopy(titleBytes, 0, title128, 0, titleBytes.length);
        } else {
            System.arraycopy(titleBytes, 0, title128, 0, 128);
        }
        System.arraycopy(title128, 0, data, 12, 128);
        title128 = new byte[128];
        titleBytes = this.album.getBytes();
        if (titleBytes.length <= 128) {
            System.arraycopy(titleBytes, 0, title128, 0, titleBytes.length);
        } else {
            System.arraycopy(titleBytes, 0, title128, 0, 128);
        }
        System.arraycopy(title128, 0, data, 140, 128);

        title128 = new byte[128];
        titleBytes = this.artist.getBytes();
        if (titleBytes.length <= 128) {
            System.arraycopy(titleBytes, 0, title128, 0, titleBytes.length);
        } else {
            System.arraycopy(titleBytes, 0, title128, 0, 128);
        }
        System.arraycopy(title128, 0, data, 268, 128);

        title128 = new byte[128];
        titleBytes = this.name.getBytes();
        if (titleBytes.length <= 128) {
            System.arraycopy(titleBytes, 0, title128, 0, titleBytes.length);
        } else {
            System.arraycopy(titleBytes, 0, title128, 0, 128);
        }
        System.arraycopy(title128, 0, data, 396, 128);
        return data;
    }

    public byte[] toSendByte() {
        return (byte[]) Utils.toSendBytes(this.mType, this.mSubType, toBytes());
    }

    public String toString() {
        return "index=" + this.index + ",type=" + this.type + ",id=" + this.id + ",name=" + this.name;
    }
//mediaList数据帧封装
public class MediaList implements DataBase {
    public static int bytesTotal = 532;

    public int start = 1;
    public int count = 1;
    public List<MediaMetaData> medias = new ArrayList();

    private int subType = 0x02;
    private int type = 0x03;

    public void getDataFromBytes(byte[] data) {
        this.start = Utils.bytesToInt(data, 0);
        this.count = Utils.bytesToInt(data, 4);
        int i = 0;
        //循环遍历所有的数据
        while (i < this.count) {
            MediaMetaData Meta = new MediaMetaData();
            byte[] mediadData = new byte[MediaMetaData.bytesTotal];
            System.arraycopy(data, MediaMetaData.bytesTotal * i + 8, mediadData, 0, MediaMetaData.bytesTotal);
            Meta.getDataFromBytes(mediadData);
            this.medias.add(Meta);
            i += 1;
        }
    }

    public byte[] toBytes() {
        byte[] data = new byte[this.medias.size() * MediaMetaData.bytesTotal + 8];
        System.arraycopy(Utils.intToBytes(this.start), 0, data, 0, 4);
        System.arraycopy(Utils.intToBytes(this.count), 0, data, 4, 4);
        int i = 0;
        while (i < this.medias.size()) {
            System.arraycopy(((MediaMetaData) this.medias.get(i)).toBytes(), 0, data, MediaMetaData.bytesTotal * i + 8, MediaMetaData.bytesTotal);
            i += 1;
        }
        return data;
    }

    public byte[] toSendByte() {
        return Utils.toSendBytes(this.type, this.subType, toBytes());
    }

    public String toString() {
        String str = "";
        int i = 0;
        while (i < this.medias.size()) {
            str = str + "," + ((MediaMetaData) this.medias.get(i)).name;
            i += 1;
        }
        return "musics =" + str;
    }
}
 // 完整帧组成
  public static byte[] toSendBytes(int type, int subType, byte[] data) {
        int allLength = byteHead.length + 4 + 4 + 4 + 4 + data.length + byteTail.length;
        int dataLength = data.length;
        byte[] subType1 = new byte[4];
        byte[] sendData = new byte[allLength];
        System.arraycopy(byteHead, 0, sendData, 0, 4);
        System.arraycopy(intToBytes(type), 0, sendData, 4, 4);
        System.arraycopy(intToBytes(subType), 0, sendData, 8, 4);
        System.arraycopy(subType1, 0, sendData, 12, 4);
        System.arraycopy(intToBytes(dataLength), 0, sendData, 16, 4);
        System.arraycopy(data, 0, sendData, 20, dataLength);
        System.arraycopy(byteTail, 0, sendData, dataLength + 20, 4);
        return sendData;
    }

主要是用System.arraycopy来截取字节数组，重新组合或者重新分离。