java文件上传大小的基础处理

主要用于java中上传时对文件大小的处理,往数据库中存的时候比较方便、取的时候也有处理，还有基础的加减乘除：

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * getSize(String str)---是将初始大小转化为常见单位
 * getRealNum(String str)---是将常见单位转换为初始大小(默认单位为B)
 * plus(String str1,String str2)--是将常见单位相加(str1 + str2)
 * subtract(String str1,String str2)--是将常见单位相减(str1 - str2)
 * multiply(String str1,String str2)--是将常见单位相乘(str1 * str2)
 * divide(String str1,String str2)--是将常见单位相除(str1 / str2)
 * @author lyf
 * @parameter string
 */
public class FileSizeUtil{
	/**
	 * 加法
	 * @param str1
	 * @param str2
	 * @return str1+str2
	 */
	public static String plus(String str1,String str2){
		long numa = getRealNum(str1);
		long numb = getRealNum(str2);
		return getSize(numa + numb);
	} 
	
	/**
	 * 减法
	 * @param str1
	 * @param str2
	 * @return str1-str2
	 */
	public static String subtract(String str1,String str2){
		long numa = getRealNum(str1);
		long numb = getRealNum(str2);
		return getSize(numa - numb);
	}
	
	/**
	 * 乘法
	 * @param str1
	 * @param str2
	 * @return str1*str2
	 */
	public static String multiply(String str1,String str2){
		long numa = getRealNum(str1);
		long numb = getRealNum(str2);
		return getSize(numa * numb);
	}
	
	/**
	 * 除法
	 * @param str1
	 * @param str2
	 * @return str1/str2
	 */
	public static String divide(String str1,String str2){
		long numa = getRealNum(str1);
		long numb = getRealNum(str2);
		return getSize(numa / numb);
	}
	
	//获取数
	private static String getNums(String str){
		String num = null;
		List<String> list = getList(str);
		for(int i = 0;i < list.size();i++){
			String a = list.get(i);
			if(isNumber(a)){
				num = a;
			}
		}
		return num;
	}
	
	// 获取单位
	private static String getUnits(String str){
		String unit = null;
		List<String> list = getList(str);
		for(int i = 0;i < list.size();i++){
			String a = list.get(i);
			if(isLetter(a)){
				unit = a;
			}
		}
		return unit;
	}
	
	/**
	 * 转换常见单位为初始大小
	 * @param num
	 * @param unit
	 * @return realNum
	 */
	public static Long getRealNum(String str){
		String unit = getUnits(str);
		String num = getNums(str);
		long realNum = 0;
		Long[] nums = {getNum(0),getNum(1),getNum(2),getNum(3),getNum(4)};
		String[] units = {"B","KB","MB","GB","TB"};
		for(int k = 0;k < units.length;k++){
			if(unit.toUpperCase().equals(units[k])){
				long n = (long)Integer.parseInt(num);
				realNum = n * nums[k];
			}
		}
		return realNum;
	}
	
	// 1024的n次方
	private static Long getNum(int n){
		return (long)Math.pow(1024, n);
	}
	
        //分离英语和数字
	private static List<String> getList(String str){
		List<String> list = new ArrayList<String>();

		String s = "\\d+.\\d|\\w+";
		Pattern pattern = Pattern.compile(s);
		Matcher ma = pattern.matcher(str);
		while(ma.find()){
			list.add(ma.group());
		}
		return list;
	}
	
	//判断是否是数字
	private static boolean isNumber(String str){
		return isTrue("\\d+",str);
	}
	//判断是否是字母
	private static boolean isLetter(String str){
		return isTrue("\\w+",str);
	}
	
	//判断--传入正则表达式
	private static boolean isTrue(String reg,String str){		
		Pattern pattern = Pattern.compile(reg);
		Matcher ma = pattern.matcher(str);
		while(ma.find()){
			return true;
		}
		return false;
	}
	
	/**
	 * 转换初始大小为常见单位
	 * @param size
	 * @return
	 */
	public static String getSize(long size){
		final long unit = 1024;
		java.text.DecimalFormat df = new java.text.DecimalFormat("#.##");
		
		String[] units = {"B","KB","MB","GB","TB"};
		for(int i = 0;i < units.length;i++){
			double d = getNumSize(size,i);
			if(d < unit){
				return df.format(d) + units[i];
			}
		}
		return null;
	}
	//单位换算
	private static double getNumSize(long size,int n){
		double d = size / Math.pow(1024, n);
		return d;
	}
	//test
	public static void main(String[] args){
		System.out.println(isNumber("123"));
		System.out.println(isLetter("aa"));
		System.out.println("转换为初始大小：" + getRealNum("234MB"));
		System.out.println("两字符串单位相加：" + plus("123MB","1024KB"));
		System.out.println("小写字母的字符串相加：" + plus("123mb","1024kb"));
	}
}