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Java隨機產生字元串
java生成隨機字元串，主要是先建立一個26字元的字元串，然後使用random類來隨機選擇，拼接成一個新的字元串，如下代碼：
package com.qiu.lin.he; import java.util.Random; public class Ceshi { public static void main(String[] args) { System.out.println(getRandomString(10));//調用隨機生成字元串的方法，並列印出來 } public static String getRandomString(int length) { String str = “abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789”;//含有字元和數字的字元串 Random random = new Random();//隨機類初始化 StringBuffer sb = new StringBuffer();//StringBuffer類生成，為了拼接字元串 for (int i = 0; i length; ++i) { int number = random.nextInt(62);// [0,62) sb.append(str.charAt(number)); } return sb.toString(); }}
在java語言中如何隨機地生成一個字元串
可以配合UUID或者GUID來實現
GUID是一個128位長的數字，一般用16進位表示。演算法的核心思想是結合機器的網卡、當地時間、一個隨機數來生成GUID。從理論上講，如果一台機器每秒產生10000000個GUID，則可以保證（概率意義上）3240年不重複。
UUID是1.5中新增的一個類，在java.util下，用它可以產生一個號稱全球唯一的ID
import java.util.UUID;
public class Test {
public static void main(String[] args) {
UUID uuid = UUID.randomUUID();
System.out.println (uuid);
}
}
編譯運行輸出：
07ca3dec-b674-41d0-af9e-9c37583b08bb
兩種方式生成guid 與uuid
需要comm log 庫
/**
* @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隨機生成字元串
代碼如下：
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();
}
}
代碼解讀：
調用getRandomString（）方法時的length參數為要返回的隨機字元串的長度。
StringBuffer buffer = new StringBuffer(“0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ”);
0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
此段字元串代表要出現的字元還可以是其他字元
如：- + = * 。.等等
Java隨機生成字元串
代碼如下，供參考：
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++) {
// 這種寫法易於擴展，chs內容改了不用修改代碼
str += chs[random.nextInt(chs.length)];
}
str += random.nextInt(10);
return str;
}
}
java怎麼隨機生成一個字元串？
/**
* 產生隨機字元串
* */
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);
}
//調用此方法randomString(int),int是字元串的長度，即可產生指定長度的隨機字元串。
原創文章，作者：小藍，如若轉載，請註明出處：https://www.506064.com/zh-tw/n/154357.html
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