Java long 轉換成字節

Question

我正在嘗試將 long 轉換為字節數組以通過 BLE 消息發送出去。 我嘗試了幾種不同的方法，但未能成功將數據從 long 轉換為字節。 我讀的時間很長，然后我想轉換成一個字節，但保持數字如下所示：

// 例如 long -> 1620903871 long tsLong = System.currentTimeMillis()/1000;

               byte[] outgoingbytes = new byte[10];
               // this is the outcome of the data conversion and this how the data needs to presented in the bytes
               outgoingbytes[0] = 1;
               outgoingbytes[1] = 6;
               outgoingbytes[2] = 2;
               outgoingbytes[3] = 0;
               outgoingbytes[4] = 9;
               outgoingbytes[5] = 0;
               outgoingbytes[6] = 3;
               outgoingbytes[7] = 8;
               outgoingbytes[8] = 7;
               outgoingbytes[1] = 1;

目前，當我將其轉換為 ASCII 時，不能只獲得原始數字。 任何想法如何長成字節？

Answer 1

看一下 Java 的 DataInput 和 DataOutput 接口及其實現：

數據輸入流：

public final long readLong() throws IOException {
    readFully(readBuffer, 0, 8);
    return (((long)readBuffer[0] << 56) +
            ((long)(readBuffer[1] & 255) << 48) +
            ((long)(readBuffer[2] & 255) << 40) +
            ((long)(readBuffer[3] & 255) << 32) +
            ((long)(readBuffer[4] & 255) << 24) +
            ((readBuffer[5] & 255) << 16) +
            ((readBuffer[6] & 255) <<  8) +
            ((readBuffer[7] & 255) <<  0));
}

數據輸出流：

/**
 * Writes a <code>long</code> to the underlying output stream as eight
 * bytes, high byte first. In no exception is thrown, the counter
 * <code>written</code> is incremented by <code>8</code>.
 *
 * @param      v   a <code>long</code> to be written.
 * @exception  IOException  if an I/O error occurs.
 * @see        java.io.FilterOutputStream#out
 */
public final void writeLong(long v) throws IOException {
    writeBuffer[0] = (byte)(v >>> 56);
    writeBuffer[1] = (byte)(v >>> 48);
    writeBuffer[2] = (byte)(v >>> 40);
    writeBuffer[3] = (byte)(v >>> 32);
    writeBuffer[4] = (byte)(v >>> 24);
    writeBuffer[5] = (byte)(v >>> 16);
    writeBuffer[6] = (byte)(v >>>  8);
    writeBuffer[7] = (byte)(v >>>  0);
    out.write(writeBuffer, 0, 8);
    incCount(8);
}