需要幫助才能理解java中的一段代碼

Question

static long nextPowerOf2(long n) 
{ 
    n--; 
    n |= n >> 1; 
    n |= n >> 2; 
    n |= n >> 4; 
    n |= n >> 8; 
    n |= n >> 16; 
    n++; 
    return n; 
} 

我正在閱讀博客中的Java代碼示例。我正在面對的難以理解這個代碼。請解釋一下這個函數的功能是什麼？

Answer 1

正如方法的名稱所暗示的，它返回的下一個最近的和大於n數是2。

你需要運行自己這個代碼，添加打印語句，看到的中間結果的力量代碼執行。

如果調用方法nextPowerOf2(6)這究竟會發生的方法裏面：

n--; // n becomes 5; 
n |= n >> 1; // This is equivalent to n = n | n >> 1. 
      // Bit shift >> has higher precedence than bitwise OR |. 
      // This is why it becomes 7. Try it yourself and read about 
      // these operators. 
n |= n >> 2; // n is 7 
n |= n >> 4; // n is 7 
n |= n >> 8; // n is 7 
n |= n >> 16; // n is 7 
n++; // n is 8 
return n; // return n which is equal to 8 - the next nearest to 6 power of 2. 

希望這有助於。