1: 时间戳是当前时间到1970年的毫秒数。
你非要12位可以 :
new Date().getTime()-1300000000000L
这个数至少100年还是12位。而且不会重复
时间戳高并发还是会有重复的,你应该每获取一次加1的方法生成。用锁对象或者把方法声明为synchronized保证并发也不会重复。如果有用数据库,也可以用数据库提供的sequence来帮你生成
抽取一个方法
这种一般都是序号吧 或者一段字符加上序号 每次取得时候加一
java应该用UUID.
或者数据库上SEQ实现
Calendar calendar = Calendar.getInstance();
System.out.println("现在:"+calendar.getTime().getTime());
calendar.add(Calendar.YEAR, 10);
System.out.println("10年后:"+calendar.getTime().getTime());
输出:
现在:1404208483914
10年后:1719827683914
如果用时间戳,截取后面12位,不要第一位,18年内都不会有大问题,不过这样的话,你的生成ID的方法就得同步,避免高并发的时候可能出现的相同ID(理论上很有可能的,虽然1毫秒内出现生成多个订单的几率很小)
package com.tangkuo.utils;
import java.util.Date;
import java.util.UUID;
public class TestNums {
public static void main(String[] args) {
long time = new Date().getTime()-1300000000000L;
System.out.println("=" + time);
System.out.println("System.currentTimeMillis()1 = " + System.currentTimeMillis());
System.out.println("UUID.randomUUID() = " + UUID.randomUUID());
System.out.println("System.currentTimeMillis()2 = " + System.currentTimeMillis());
}
}
package com.iec.app.utils;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
public class RandomId {
private Random random;
private String table;
private static final int radLength =15;
private static final String[] radArr = new String[]{"A","B","C","D","E","F","G","H","I","G","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
public RandomId() {
random = new Random();
table = "0123456789";
}
public String randomId(long id) {
String ret = null,num = String.format("%05d", id);
int key = random.nextInt(10),seed = random.nextInt(100);
Caesar caesar = new Caesar(table, seed);
num = caesar.encode(key, num);
ret = num + String.format("%01d", key) + String.format("%02d", seed);
// 加入生成的随机字符
/* int letterSize = radLength - ret.length();
for(int i=0;i<letterSize;i++){
String letter = radArr[ random.nextInt(radArr.length)];
int index = random.nextInt(ret.length());
ret = ret.substring(0, index) + letter + ret.substring(index, ret.length());
}*/
return ret;
}
public static void main(String[] args) {
RandomId r = new RandomId();
System.out.println(r.randomId(12));
}
}
package com.iec.app.utils;
/**
*
* @author
*
*/
public class Caesar {
private String table;
private int seedA = 1103515245;
private int seedB = 12345;
public Caesar(String table, int seed) {
this.table = chaos(table, seed, table.length());
}
public Caesar(String table) {
this(table, 11);
}
public Caesar() {
this(11);
}
public Caesar(int seed) {
this("ABCDEFGHIJKLMNOPQRSTUVWXYZ", seed);
}
public char dict(int i, boolean reverse) {
int s = table.length(), index = reverse ? s - i : i;
return table.charAt(index);
}
public int dict(char c, boolean reverse) {
int s = table.length(), index = table.indexOf(c);
return reverse ? s - index : index;
}
public int seed(int seed) {
long temp = seed;
return (int)((temp * seedA + seedB) & 0x7fffffffL);
}
public String chaos(String data, int seed, int cnt) {
StringBuffer buf = new StringBuffer(data);
char tmp; int a, b, r = data.length();
for (int i = 0; i < cnt; i += 1) {
seed = seed(seed); a = seed % r;
seed = seed(seed); b = seed % r;
tmp = buf.charAt(a);
buf.setCharAt(a, buf.charAt(b));
buf.setCharAt(b, tmp);
}
return buf.toString();
}
public String crypto(boolean reverse,
int key, String text) {
String ret = null;
StringBuilder buf = new StringBuilder();
int m, s = table.length(), e = text.length();
for(int i = 0; i < e; i += 1) {
m = dict(text.charAt(i), reverse);
if (m < 0) break;
m = m + key + i;
buf.append(dict(m % s, reverse));
}
if (buf.length() == e)
ret = buf.toString();
return ret;
}
public String encode(int key, String text) {
return crypto(false, key, text);
}
public String decode(int key, String text) {
return crypto(true , key, text);
}
public static void main(String[] args) {
Caesar caesar = new Caesar();
String data = caesar.encode(32, "APPLE");
caesar.decode(32, data);
}
}
12唯一订单号生成 方法总结
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转载自tangkuo.iteye.com/blog/2306770
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