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java随机生成字符串和校验(java字符串格式校验)

本文目录一览:

Java随机产生字符串

java生成随机字符串,主要是先建立一个26字符的字符串,然后使用random类来随机选择,拼接成一个新的字符串,如下代码:

package com.qiu.lin.he; import java.util.Random; public class Ceshi { public static void main(String[] args) { System.out.println(getRandomString(10));//调用随机生成字符串的方法,并打印出来 } public static String getRandomString(int length) { String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";//含有字符和数字的字符串 Random random = new Random();//随机类初始化 StringBuffer sb = new StringBuffer();//StringBuffer类生成,为了拼接字符串 for (int i = 0; i length; ++i) { int number = random.nextInt(62);// [0,62) sb.append(str.charAt(number)); } return sb.toString(); }}

在java语言中如何随机地生成一个字符串

可以配合UUID或者GUID来实现

GUID是一个128位长的数字,一般用16进制表示。算法的核心思想是结合机器的网卡、当地时间、一个随机数来生成GUID。从理论上讲,如果一台机器每秒产生10000000个GUID,则可以保证(概率意义上)3240年不重复。

UUID是1.5中新增的一个类,在java.util下,用它可以产生一个号称全球唯一的ID

import java.util.UUID;

public class Test {

public static void main(String[] args) {

UUID uuid = UUID.randomUUID();

System.out.println (uuid);

}

}

编译运行输出:

07ca3dec-b674-41d0-af9e-9c37583b08bb

两种方式生成guid 与uuid

需要comm log 库

/**

* @author Administrator

*

* TODO To change the template for this generated type comment go to

* Window - Preferences - Java - Code Style - Code Templates

*/

import java.net.InetAddress;

import java.net.UnknownHostException;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.util.Random;

public class RandomGUID extends Object {

protected final org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory

.getLog(getClass());

public String valueBeforeMD5 = "";

public String valueAfterMD5 = "";

private static Random myRand;

private static SecureRandom mySecureRand;

private static String s_id;

private static final int PAD_BELOW = 0x10;

private static final int TWO_BYTES = 0xFF;

/*

* Static block to take care of one time secureRandom seed.

* It takes a few seconds to initialize SecureRandom. You might

* want to consider removing this static block or replacing

* it with a "time since first loaded" seed to reduce this time.

* This block will run only once per JVM instance.

*/

static {

mySecureRand = new SecureRandom();

long secureInitializer = mySecureRand.nextLong();

myRand = new Random(secureInitializer);

try {

s_id = InetAddress.getLocalHost().toString();

} catch (UnknownHostException e) {

e.printStackTrace();

}

}

/*

* Default constructor. With no specification of security option,

* this constructor defaults to lower security, high performance.

*/

public RandomGUID() {

getRandomGUID(false);

}

/*

* Constructor with security option. Setting secure true

* enables each random number generated to be cryptographically

* strong. Secure false defaults to the standard Random function seeded

* with a single cryptographically strong random number.

*/

public RandomGUID(boolean secure) {

getRandomGUID(secure);

}

/*

* Method to generate the random GUID

*/

private void getRandomGUID(boolean secure) {

MessageDigest md5 = null;

StringBuffer sbValueBeforeMD5 = new StringBuffer(128);

try {

md5 = MessageDigest.getInstance("MD5");

} catch (NoSuchAlgorithmException e) {

logger.error("Error: " + e);

}

try {

long time = System.currentTimeMillis();

long rand = 0;

if (secure) {

rand = mySecureRand.nextLong();

} else {

rand = myRand.nextLong();

}

sbValueBeforeMD5.append(s_id);

sbValueBeforeMD5.append(":");

sbValueBeforeMD5.append(Long.toString(time));

sbValueBeforeMD5.append(":");

sbValueBeforeMD5.append(Long.toString(rand));

valueBeforeMD5 = sbValueBeforeMD5.toString();

md5.update(valueBeforeMD5.getBytes());

byte[] array = md5.digest();

StringBuffer sb = new StringBuffer(32);

for (int j = 0; j array.length; ++j) {

int b = array[j] TWO_BYTES;

if (b PAD_BELOW)

sb.append('0');

sb.append(Integer.toHexString(b));

}

valueAfterMD5 = sb.toString();

} catch (Exception e) {

logger.error("Error:" + e);

}

}

/*

* Convert to the standard format for GUID

* (Useful for SQL Server UniqueIdentifiers, etc.)

* Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6

*/

public String toString() {

String raw = valueAfterMD5.toUpperCase();

StringBuffer sb = new StringBuffer(64);

sb.append(raw.substring(0, 8));

sb.append("-");

sb.append(raw.substring(8, 12));

sb.append("-");

sb.append(raw.substring(12, 16));

sb.append("-");

sb.append(raw.substring(16, 20));

sb.append("-");

sb.append(raw.substring(20));

return sb.toString();

}

// Demonstraton and self test of class

public static void main(String args[]) {

for (int i=0; i 100; i++) {

RandomGUID myGUID = new RandomGUID();

System.out.println("Seeding String=" + myGUID.valueBeforeMD5);

System.out.println("rawGUID=" + myGUID.valueAfterMD5);

System.out.println("RandomGUID=" + myGUID.toString());

}

}

}

java随机生成字符串

代码如下:

import java.util.Random;

public class Demo {

public static void main(String args[]){

Demo demo = new Demo();

System.out.println(demo.getRandomString(20));

}

public static String getRandomString(int length) {

StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

StringBuffer sb = new StringBuffer();

Random random = new Random();

int range = buffer.length();

for (int i = 0; i length; i ++) {

sb.append(buffer.charAt(random.nextInt(range)));

}

return sb.toString();

}

}

代码解读:

调用getRandomString()方法时的length参数为要返回的随机字符串的长度。

StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

此段字符串代表要出现的字符还可以是其他字符

如:- + = * 。.等等

Java随机生成字符串

代码如下,供参考:

import java.util.Random;

public class Main {

    public static void main(String[] args) {

        char[] chs = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',

                'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

        String str = new Main().getStr(chs);

        System.out.println(str);

    }

    public String getStr(char[] chs) {

        String str = "";

        Random random = new Random();

        for (int i = 0; i  4; i++) {

                // 这种写法易于扩展,chs内容改了不用修改代码

            str += chs[random.nextInt(chs.length)];

        }

        str += random.nextInt(10);

        return str;

    }

}

java怎么随机生成一个字符串?

/**

* 产生随机字符串

* */

private static Random randGen = null;

private static char[] numbersAndLetters = null;

public static final String randomString(int length) {

if (length 1) {

return null;

}

if (randGen == null) {

randGen = new Random();

numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyz" +

"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();

//numbersAndLetters = ("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();

}

char [] randBuffer = new char[length];

for (int i=0; irandBuffer.length; i++) {

randBuffer[i] = numbersAndLetters[randGen.nextInt(71)];

//randBuffer[i] = numbersAndLetters[randGen.nextInt(35)];

}

return new String(randBuffer);

}

//调用此方法randomString(int),int是字符串的长度,即可产生指定长度的随机字符串。