生成流水号

package com.byd.core;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;

import freemarker.template.SimpleDate;

public class RandomUtils { 
    public static final String allChar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
    public static final String letterChar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
    public static final String numberChar = "0123456789";

    /** 
     * 返回一个定长的随机字符串(只包含大小写字母、数字) 
     * 
     * @param length 随机字符串长度 
     * @return 随机字符串 
     */ 
    public static String generateString() { 
            StringBuffer sb = new StringBuffer(); 
            Random random = new Random(); 
            for (int i = 0; i <=2; i++) { 
                    sb.append(numberChar.charAt(random.nextInt(numberChar.length()))); 
            } 
            return sb.toString(); 
    }
    public static String getDateString(){
    	@SuppressWarnings("unused")
    	Date date = new Date();
    	DateFormat format = new SimpleDateFormat("yyyyMMdd");
    	String reTime = format.format(date);
    	StringBuffer sb= new StringBuffer(reTime);
    	String nDate=sb.substring(2, 8);
    	return nDate;
    }
    public static String getZD(String strName){
    	if(strName.equals("计划")){
    		return "JH";
    	}else if(strName.equals("生产")){
    		return "SC";
    	}else if(strName.equals("工艺")){
    		return "工艺";
    	}else if(strName.equals("宝龙")){
    		return "BL";
    	}else if(strName.equals("上海")){
    		return "SH";
    	}else if(strName.equals("北京")){
    		return "BJ";
    	}else if(strName.equals("葵涌")){
    		return "KC";
    	}else{
    		return "error";
    	}
    }
    
    public static String getFuction(String strName){
    	if(strName.equals("发布")){
    		return "FB";
    	}else if(strName.equals("报废")){
    		return "BF";
    	}else if(strName.equals("冲销")){
    		return "CX";
    	}else if(strName.equals("清理")){
    		return "QL";
    	}else if(strName.equals("调拨")){
    		return "DB";
    	}else if(strName.equals("借用")){
    		return "JY";
    	}else if(strName.equals("送样")){
    		return "SY";
    	}else if(strName.equals("试产")){
    		return "SC";
    	}else if(strName.equals("借出")){
    		return "JC";
    	}else{
    		return "error";
    	}
    }
    
    public static String getBicker(String str,String str1){
    	String str2=RandomUtils.getZD(str);
    	String str3=RandomUtils.getFuction(str1);
    	String date=RandomUtils.getDateString();
    	String num=RandomUtils.generateString();
    	StringBuffer bf = new StringBuffer(str2);
    	bf.append(str3);
    	bf.append(date);
    	String bicker=bf.append(num).toString();
    	return bicker;
    }

    /** 
     * 返回一个定长的随机纯字母字符串(只包含大小写字母) 
     * 
     * @param length 随机字符串长度 
     * @return 随机字符串 
     */ 
    public static String generateMixString(int length) { 
            StringBuffer sb = new StringBuffer(); 
            Random random = new Random(); 
            for (int i = 0; i < length; i++) { 
                    sb.append(allChar.charAt(random.nextInt(letterChar.length()))); 
            } 
            return sb.toString(); 
    }

    /** 
     * 返回一个定长的随机纯大写字母字符串(只包含大小写字母) 
     * 
     * @param length 随机字符串长度 
     * @return 随机字符串 
     */ 
    public static String generateLowerString(int length) { 
            return generateMixString(length).toLowerCase();
    }

    /** 
     * 返回一个定长的随机纯小写字母字符串(只包含大小写字母) 
     * 
     * @param length 随机字符串长度 
     * @return 随机字符串 
     */ 
    public static String generateUpperString(int length) { 
            return generateMixString(length).toUpperCase(); 
    }

    /** 
     * 生成一个定长的纯0字符串 
     * 
     * @param length 字符串长度 
     * @return 纯0字符串 
     */ 
    public static String generateZeroString(int length) { 
            StringBuffer sb = new StringBuffer(); 
            for (int i = 0; i < length; i++) { 
                    sb.append('0'); 
            } 
            return sb.toString(); 
    }

    /** 
     * 根据数字生成一个定长的字符串，长度不够前面补0 
     * 
     * @param num             数字 
     * @param fixdlenth 字符串长度 
     * @return 定长的字符串 
     */ 
    public static String toFixdLengthString(long num, int fixdlenth) { 
            StringBuffer sb = new StringBuffer(); 
            String strNum = String.valueOf(num); 
            if (fixdlenth - strNum.length() >= 0) { 
                    sb.append(generateZeroString(fixdlenth - strNum.length())); 
            } else { 
                    throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！"); 
            } 
            sb.append(strNum); 
            return sb.toString(); 
    }

    /** 
     * 根据数字生成一个定长的字符串，长度不够前面补0 
     * 
     * @param num             数字 
     * @param fixdlenth 字符串长度 
     * @return 定长的字符串 
     */ 
    public static String toFixdLengthString(int num, int fixdlenth) { 
            StringBuffer sb = new StringBuffer(); 
            String strNum = String.valueOf(num); 
            if (fixdlenth - strNum.length() >= 0) { 
                    sb.append(generateZeroString(fixdlenth - strNum.length())); 
            } else { 
                    throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！"); 
            } 
            sb.append(strNum); 
            return sb.toString(); 
    }

    public static void main(String[] args) { 
    		System.out.println(getDateString());
            System.out.println(generateString()); 
           // System.out.println(getBicker());
            System.out.println(generateMixString(15)); 
            System.out.println(generateLowerString(15)); 
            System.out.println(generateUpperString(15)); 
            System.out.println(generateZeroString(15)); 
            System.out.println(toFixdLengthString(123, 15)); 
            System.out.println(toFixdLengthString(123L, 15)); 
    } 
}