Java 生成不重复的编号

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package com.cn;

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

/**
 * 随机生成编号
 * @author JC
 *
 */
public class Test01 {
	
	/** 用户id和随机数总长度 */
    private static final int maxLength = 5;

    /** 随即编码 */
    private static final int[] code = new int[]{7, 9, 6, 2, 8 , 1, 3, 0, 5, 4};
    
    /**  
     * 更具id进行加密+加随机数组成固定长度编码
     */
    private static String toCode(Long id) {
        String idStr = id.toString();
        StringBuilder idsbs = new StringBuilder();
        for (int i = idStr.length() - 1 ; i >= 0; i--) {
            idsbs.append(code[idStr.charAt(i)-'0']);
        }
        return idsbs.append(getRandom(maxLength - idStr.length())).toString();
    }
     
    /**
     * 生成时间戳
     */
    private static String getDateTime(){
        DateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
        return sdf.format(new Date());
    }
    
    /**
     * 生成固定长度随机码
     * @param len 长度
     */
    private static long getRandom(long len) {
        long min = 1,max = 9; 
        for (int i = 1; i < len; i++) {
            min *= 10;
            max *= 10;
        }
        long rangeLong = (((long) (new Random().nextDouble() * (max - min)))) + min ;
        return rangeLong;
    }
    
    /**
     * 生成不带类别标头的编码
     * @param id
     */
    private static synchronized String getCode(){
    	//id = id == null ? 1000 : id;
    	int count = 0;
    	String result = "";
    	try {
    		Random random = new Random();  
            for(int i = 0; i < 100; i++)  
            {  
            	count = random.nextInt(51) + 10; 
            }  
            result = getDateTime() + toCode(Long.valueOf(count)); 
		} catch (Exception e) {
			e.printStackTrace();
		} 
    	return result;
    } 
  
    public static void main(String[] args) {
		System.out.println(getCode());

	}
	
}