Question

我如何以一种他们完全理解它的方式向一类Java Card初学者解释这段代码：

private void getBalance(APDU apdu) {
    byte[] buffer = apdu.getBuffer();

    // inform system that the applet has finished
    // processing the command and the system should
    // now prepare to construct a response APDU
    // which contains data field
    short le = apdu.setOutgoing();

    if (le < 2) {
        ISOException.throwIt((byte) 0x6A86);
    }

    // informs the CAD the actual number of bytes
    // returned
    apdu.setOutgoingLength((byte) 2);

    // move the balance data into the APDU buffer
    // starting at the offset 0
    buffer[0] = (byte) (balance >> 8);

    buffer[1] = (byte) (balance & 0xFF);//How do i explain what happens here



    // send the 2-byte balance at the offset
    // 0 in the apdu buffer
    apdu.sendBytes((short) 0, (short) 2);
}

Answer 1

解释整数的二进制表示。解释＆gt;＆gt;转移运营商。解释十六进制符号，以及0xFF变为什么。解释按位和/或运算符。将它们放在一起以显示＆gt;＆gt; 8和＆amp; 0xFF的组合如何将16位值分成高字节和低字节。询问是否有任何问题。

解释二元运算符'＆amp;'的方式适用于Java Card

1 个答案: