Java常用工具类---数字工具类

package com.jarvis.base.util;

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Random;


public class NumericHelper {

	/**
	 * 描述：通过一个整数i获取你所要的哪几个(从0开始) i为 多个2的n次方之和，如i=7，那么根据原值是2的n次方之各，你的原值必定是1，2，4 。
	 * 
	 * @param i
	 *            数值
	 * @return
	 */
	public static int[] getWhich(long i) {
		int exp = Math.getExponent(i);
		if (i == (1 << (exp + 1)) - 1) {
			exp = exp + 1;
		}
		int[] num = new int[exp];
		int x = exp - 1;
		for (int n = 0; (1 << n) < i + 1; n++) {
			if ((1 << (n + 1)) > i && (1 << n) < (i + 1)) {
				num[x] = n;
				i -= 1 << n;
				n = 0;
				x--;
			}
		}
		return num;
	}

	/**
	 * 描述：非四舍五入取整处理
	 * 
	 * @param v
	 *            需要四舍五入的数字
	 * @return
	 */
	public static int roundDown(double v) {
		BigDecimal b = new BigDecimal(Double.toString(v));
		BigDecimal one = new BigDecimal("1");
		return b.divide(one, 0, BigDecimal.ROUND_DOWN).intValue();
	}

	/**
	 * 描述：四舍五入取整处理
	 * 
	 * @param v
	 *            需要四舍五入的数字
	 * @return
	 */
	public static int roundUp(double v) {
		BigDecimal b = new BigDecimal(Double.toString(v));
		BigDecimal one = new BigDecimal("1");
		return b.divide(one, 0, BigDecimal.ROUND_UP).intValue();
	}

	/**
	 * 描述：提供精确的小数位四舍五入处理。
	 * 
	 * @param v
	 *            需要四舍五入的数字
	 * @param scale
	 *            小数点后保留几位
	 * @return 四舍五入后的结果
	 */
	public static double round(double v, int scale) {
		if (scale < 0) {
			throw new IllegalArgumentException("The scale must be a positive integer or zero");
		}

		BigDecimal b = new BigDecimal(Double.toString(v));
		BigDecimal one = new BigDecimal("1");
		return b.divide(one, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
	}

	/**
	 * 描述：四舍五入保留两位小数
	 * 
	 * @param num
	 *            数字
	 * @return 保留两位小数的数字字串
	 */
	public static String format(double num) {
		return format(num, "0.00");
	}

	/**
	 * 描述：四舍五入数字保留小数位
	 * 
	 * @param num
	 *            数字
	 * @param digits
	 *            小数位
	 * @return
	 */
	public static String format(double num, int digits) {
		String pattern = "0";
		if (digits > 0) {
			pattern += "." + createStr("0", digits, "");
		}
		return format(num, pattern);
	}

	/**
	 * 描述：生成字符串
	 * 
	 * @param arg0
	 *            字符串元素
	 * @param arg1
	 *            生成个数
	 * @param arg2
	 *            间隔符号
	 * @return
	 */
	private static String createStr(String arg0, int arg1, String arg2) {
		if (arg0 == null) {
			return "";
		} else {
			StringBuffer sb = new StringBuffer();
			for (int i = 0; i < arg1; i++) {
				if (arg2 == null)
					arg2 = "";
				sb.append(arg0).append(arg2);
			}
			if (sb.length() > 0) {
				sb.delete(sb.lastIndexOf(arg2), sb.length());
			}

			return sb.toString();
		}
	}

	/**
	 * 描述：数字格式化
	 * 
	 * @param num
	 *            数字
	 * @param pattern
	 *            格式
	 * @return
	 */
	public static String format(double num, String pattern) {
		NumberFormat fmt = null;
		if (pattern != null && pattern.length() > 0) {
			fmt = new DecimalFormat(pattern);
		} else {
			fmt = new DecimalFormat();
		}
		return fmt.format(num);
	}

	/**
	 * 求浮点数的权重
	 * 
	 * @param number
	 * @return
	 */
	public static double weight(double number) {
		if (number == 0) {
			return 1;
		}

		double e = Math.log10(Math.abs(number));
		int n = Double.valueOf(Math.floor(e)).intValue();
		double weight = 1;
		if (n > 0) {
			for (int i = 0; i < n; i++) {
				weight *= 10;
			}
		} else {
			for (int i = 0; i > n; i--) {
				weight /= 10;
			}
		}
		return weight;
	}

	/**
	 * 获得权重的单位
	 * 
	 * @param scale
	 * @return
	 */
	public static String unit(double scale) {
		if (scale == 1 || scale == 0) {
			return "";// 不设置单位倍率单位，使用基准单位
		}
		String[] units = new String[] { "十", "百", "千", "万", "十万", "百万", "千万", "亿", "十亿", "百亿", "千亿", "兆" };
		String[] units2 = new String[] { "十分", "百分", "千分", "万分", "十万分", "百万分", "千万分" };
		double e = Math.log10(scale);
		int position = Double.valueOf(Math.ceil(e)).intValue();
		if (position >= 1 && position <= units.length) {
			return units[position - 1];
		} else if (position <= -1 && -position <= units2.length) {
			return units2[-position - 1];
		} else {
			return "无量";
		}
	}

	/**
	 * 获得浮点数的缩放比例
	 * 
	 * @param num
	 * @return
	 */
	public static double scale(double num) {
		double absValue = Math.abs(num);
		// 无需缩放
		if (absValue < 10000 && absValue >= 1) {
			return 1;
		}
		// 无需缩放
		else if (absValue < 1 && absValue > 0.0001) {
			return 1;
		} else {
			return weight(num) / 10;
		}
	}

	/**
	 * 获得缩放后并且格式化的浮点数
	 * 
	 * @param num
	 * @param scale
	 * @return
	 */
	public static double scaleNumber(double num, double scale) {
		DecimalFormat df = null;
		if (scale == 1) {
			df = new DecimalFormat("#.0000");
		} else {
			df = new DecimalFormat("#.00");
		}
		double scaledNum = num / scale;
		return Double.valueOf(df.format(scaledNum));
	}

	/**
	 * 产生n位随机数 TODO:性能不要，有待优化
	 */
	public static String ramdomNumber(int n) {
		if (n <= 0) {
			throw new IllegalArgumentException("n must be positive !");
		}
		Random random = new Random();
		StringBuilder result = new StringBuilder();
		for (int i = 0; i < n; i++) {
			result.append(random.nextInt(10));
		}
		return result.toString();
	}

	/**
	 * 缩放1W倍
	 */
	public static double changeTo(double number) {
		boolean flag = false;
		if (number < 0) {
			flag = true;
		}
		double value = Math.abs(number);
		value = value / 10000.0;
		if (flag) {
			value = Double.parseDouble("-" + value);
		}
		return value;
	}

	/**
	 * 
	 * 描述：缩放比例
	 * 
	 * @param number
	 * @param scale
	 * @param points
	 * @return
	 */
	public static String scaleNumberToStr(double number, double scale, int points) {
		boolean flag = (number < 0);
		number = Math.abs(number);
		String result = "";
		DecimalFormat nbf3 = (DecimalFormat) NumberFormat.getInstance();// 默认格式
		nbf3.setGroupingUsed(false);
		nbf3.setMinimumFractionDigits(points);
		nbf3.setMaximumFractionDigits(points);
		double scaledNum = number / scale;
		result = nbf3.format(scaledNum);
		if (flag) {
			result = "-" + result;
		}
		return result;
	}
}