转移Java BitSet [英] Shifting a Java BitSet

问题描述

我使用 java.util.BitSet 来存储密集的位向量。

I am using a java.util.BitSet to store a dense vector of bits.

我想要实现一个将位向右移1的操作，类似于>>> on int。

I want to implement an operation that shifts the bits right by 1, analogous to >>> on ints.

是否存在移位 BitSet s的库函数？

Is there a library function that shifts BitSets?

如果没有，是否有比下面更好的方法？

If not, is there a better way than the below?

public static void logicalRightShift(BitSet bs) {
  for (int i = 0; (i = bs.nextSetBit(i)) >= 0;) {
    // i is the first bit in a run of set bits.

    // Set any bit to the left of the run.
    if (i != 0) { bs.set(i - 1); }

    // Now i is the index of the bit after the end of the run.
    i = bs.nextClearBit(i);  // nextClearBit never returns -1.
    // Clear the last bit of the run.
    bs.clear(i - 1);

    // 0000111100000...
    //     a   b
    // i starts off the loop at a, and ends the loop at b.
    // The mutations change the run to
    // 0001111000000...
  }
}

推荐答案

应该这样做：

BitSet shifted = bs.get(1, bs.length());

它会给你一个等于orginial的位集，但没有最低位。

It will give you a bitset equal to the orginial one, but without the lower-most bit.

编辑：

将此概括为 n 位，

BitSet shifted = bs.get(n, Math.max(n, bs.length()));

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