android/guava/src/com/google/common/math/BigIntegerMath.java
public static boolean isPowerOfTwo(BigInteger x) {
    checkNotNull(x);
    return x.signum() > 0 && x.getLowestSetBit() == x.bitLength() - 1;
  }
public static boolean isPowerOfTwo(BigInteger x) {
    checkNotNull(x);
    return x.signum() > 0 && x.getLowestSetBit() == x.bitLength() - 1;
  }
public static boolean isPowerOfTwo ( BigInteger x ) { checkNotNull ( x ) ; return x . signum ( ) > 0 && x . getLowestSetBit ( ) == x . bitLength ( ) - 1 ; }
Returns {@code true} if {@code x} represents a power of two.
Returns {