pfmiles/scanCoverageRecur.java

## scanCoverageRecur.java
/**
     * 计算扫描覆盖率的通用算法
     * cover_rate递推公式为：fn = (1 - fn-1) * N/M + fn-1 ; 其中fn是本次迭代cover_rate, fn-1是上次迭代cover_rate, N是本次抽取数量，M是集合总数,f0=0;
     */
    public static BigDecimal scanCoverageRecur(BigDecimal fn1, int N, BigInteger M, int scale) {
        if (fn1 == null)
            fn1 = new BigDecimal(0);
        BigDecimal one = new BigDecimal(1);
        BigDecimal Nb = new BigDecimal(N);
        BigDecimal Mb = new BigDecimal(M);
        return one.subtract(fn1).multiply(Nb.divide(Mb, scale + 1, RoundingMode.HALF_UP)).add(fn1)
            .setScale(scale, RoundingMode.HALF_UP);
    }
	/**
	* 计算扫描覆盖率的通用算法
	* cover_rate递推公式为：fn = (1 - fn-1) * N/M + fn-1 ; 其中fn是本次迭代cover_rate, fn-1是上次迭代cover_rate, N是本次抽取数量，M是集合总数,f0=0;
	*/
	public static BigDecimal scanCoverageRecur(BigDecimal fn1, int N, BigInteger M, int scale) {
	if (fn1 == null)
	fn1 = new BigDecimal(0);
	BigDecimal one = new BigDecimal(1);
	BigDecimal Nb = new BigDecimal(N);
	BigDecimal Mb = new BigDecimal(M);
	return one.subtract(fn1).multiply(Nb.divide(Mb, scale + 1, RoundingMode.HALF_UP)).add(fn1)
	.setScale(scale, RoundingMode.HALF_UP);
	}