[分享]Java中byte[]與基礎類型之間的轉換

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作者：qiujuer
博客：blog.csdn.net/qiujuer
網站：www.qiujuer.net
開源庫：github.com/qiujuer/Genius-Android
開源庫：github.com/qiujuer/Blink
轉載請註明出處：http://blog.csdn.net/qiujuer/article/details/45152189
------學之開源，用於開源；初學者的心態，與君共勉！

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很久沒有寫博客了，有些生疏了；一直忙着做 Blink 框架去了。
在這裏打個廣告，Blink是一款Socket協議跨平臺框架，現在提供有Java、Android、C#的版本；通過Blink能實現對Socket傳輸的異步封裝，能直接發送或接受數據，現能直接發送 byte ，String，File 等類型，可在不改動框架情況下直接擴展所需類型。

Blink開源框架鏈接

因爲在Socket的傳輸中都是 Bytes 的傳輸，所以涉及到 Java 基本類型（char、short、int、long）與byte[] 的轉化，自己總結了一下，簡單的寫了一個類。

/**
 * Bit Converter
 */
public class BitConverter {

    /**
     * Convert char to byte[]
     *
     * @param x char
     * @return bytes
     */
    public static byte[] toBytes(char x) {
        return toBytes(x, new byte[2], 0);
    }

    /**
     * Convert char to byte[]
     *
     * @param x       char
     * @param bytes   Dest bytes
     * @param bytePos Dest pos
     * @return bytes
     */
    public static byte[] toBytes(char x, byte[] bytes, int bytePos) {
        bytes[bytePos++] = (byte) (x);
        bytes[bytePos] = (byte) (x >> 8);
        return bytes;
    }


    /**
     * Convert short to byte[]
     *
     * @param x Short
     * @return bytes
     */
    public static byte[] toBytes(short x) {
        return toBytes(x, new byte[2], 0);
    }

    /**
     * Convert short to byte[]
     *
     * @param x       Short
     * @param bytes   Dest bytes
     * @param bytePos Dest pos
     * @return bytes
     */
    public static byte[] toBytes(short x, byte[] bytes, int bytePos) {
        bytes[bytePos++] = (byte) (x);
        bytes[bytePos] = (byte) (x >> 8);
        return bytes;
    }

    /**
     * Convert int to byte[]
     *
     * @param x int
     * @return bytes
     */
    public static byte[] toBytes(int x) {
        return toBytes(x, new byte[4], 0);
    }

    /**
     * Convert int to byte[]
     *
     * @param x       int
     * @param bytes   Dest bytes
     * @param bytePos Dest pos
     * @return bytes
     */
    public static byte[] toBytes(int x, byte[] bytes, int bytePos) {
        bytes[bytePos++] = (byte) (x);
        bytes[bytePos++] = (byte) (x >> 8);
        bytes[bytePos++] = (byte) (x >> 16);
        bytes[bytePos] = (byte) (x >> 24);
        return bytes;
    }

    /**
     * Convert long to byte[]
     *
     * @param x long
     * @return bytes
     */
    public static byte[] toBytes(long x) {
        return toBytes(x, new byte[8], 0);
    }

    /**
     * Convert long to byte[]
     *
     * @param x       long
     * @param bytes   Dest bytes
     * @param bytePos Dest pos
     * @return bytes
     */
    public static byte[] toBytes(long x, byte[] bytes, int bytePos) {
        bytes[bytePos++] = (byte) (x);
        bytes[bytePos++] = (byte) (x >> 8);
        bytes[bytePos++] = (byte) (x >> 16);
        bytes[bytePos++] = (byte) (x >> 24);
        bytes[bytePos++] = (byte) (x >> 32);
        bytes[bytePos++] = (byte) (x >> 40);
        bytes[bytePos++] = (byte) (x >> 48);
        bytes[bytePos] = (byte) (x >> 56);
        return bytes;
    }

    /**
     * Convert byte[] to char
     *
     * @param bytes bytes
     * @return char
     */
    public static char toChar(byte[] bytes) {
        return toChar(bytes, 0);
    }

    /**
     * Convert byte[] to char
     *
     * @param bytes bytes
     * @param index byte start index
     * @return char
     */
    public static char toChar(byte[] bytes, int index) {
        return (char) ((bytes[index + 1] << 8) | (bytes[index] & 0xff));
    }

    /**
     * Convert byte[] to short
     *
     * @param bytes bytes
     * @return short
     */
    public static short toShort(byte[] bytes) {
        return toShort(bytes, 0);
    }

    /**
     * Convert byte[] to short
     *
     * @param bytes bytes
     * @param index byte start index
     * @return short
     */
    public static short toShort(byte[] bytes, int index) {
        return (short) ((bytes[index + 1] << 8) | (bytes[index] & 0xff));
    }

    /**
     * Convert byte[] to int
     *
     * @param bytes bytes
     * @return int
     */
    public static int toInt(byte[] bytes) {
        return toInt(bytes, 0);
    }

    /**
     * Convert byte[] to int
     *
     * @param bytes bytes
     * @param index bytes start index
     * @return int
     */
    public static int toInt(byte[] bytes, int index) {
        return (((bytes[index + 3]) << 24) |
                ((bytes[index + 2] & 0xff) << 16) |
                ((bytes[index + 1] & 0xff) << 8) |
                ((bytes[index] & 0xff)));
    }

    /**
     * Convert byte[] to long
     *
     * @param bytes bytes
     * @return long
     */
    public static long toLong(byte[] bytes) {
        return toLong(bytes, 0);
    }

    /**
     * Convert byte[] to long
     *
     * @param bytes bytes
     * @param index bytes start index
     * @return long
     */
    public static long toLong(byte[] bytes, int index) {
        return ((((long) bytes[index + 7]) << 56) |
                (((long) bytes[index + 6] & 0xff) << 48) |
                (((long) bytes[index + 5] & 0xff) << 40) |
                (((long) bytes[index + 4] & 0xff) << 32) |
                (((long) bytes[index + 3] & 0xff) << 24) |
                (((long) bytes[index + 2] & 0xff) << 16) |
                (((long) bytes[index + 1] & 0xff) << 8) |
                (((long) bytes[index] & 0xff)));
    }
}

需要注意的是：無論是從基本類型轉換爲 byte[] 還是 byte[] 轉換爲基本類型， 都是採用的低位在前高位在後的形式；這個與C#的默認模式是一致的，如果你的需求是高位在前的情況則需要自己更改一下順序了。

========================================================
作者：qiujuer
博客：blog.csdn.net/qiujuer
網站：www.qiujuer.net
開源庫：github.com/qiujuer/Genius-Android
開源庫：github.com/qiujuer/Blink
轉載請註明出處：http://blog.csdn.net/qiujuer/article/details/45152189
------學之開源，用於開源；初學者的心態，與君共勉！

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