java隨機字元串
❶ java如何實現隨機輸出一個字元串，由[a-zA-Z0-9]組成 長度為4,並以數字結尾
如圖所示即可。
package test;
import java.util.Random;
public class Test{
public static void main(String[] args) {
String str = getRandomString(4);
System.out.println(str);
}
public static String getRandomString(int length) {
// 定義一個字元串（A-Z，a-z，0-9）即62位；
String str = "";
// 由Random生成隨機數
Random random = new Random();
StringBuffer sb = new StringBuffer();
// 長度為幾就循環幾減一次
for (int i = 0; i < length - 1; ++i) {
// 產生0-61的數字
int number = random.nextInt(62);
// 將產生的數字通過length次承載到sb中
sb.append(str.charAt(number));
}
//補全最後一個數字位
sb.append(random.nextInt(9));
// 將承載的字元轉換成字元串
return sb.toString();
}
}
❷ 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進製表示。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年不重復。
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 rece 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());
}
}
}
❸ java中，我想隨機獲取不重復的字元串應該怎麼辦
1.先確定字元串的長度；
2.再確定字元串包括哪些字元；//這樣可以確定字元的ASCII范圍
3.然後就有很多方法去隨機獲取字元：
把字元存放在一個Map中的value中，如：map.put(1,"字元1");map.put(2,"字元2");
map.put(3,"字元3");一次類推，通過Math.random()*字元的個數，取整就可以得到key值，
map.get(key)，value不為null,然後在map中刪除這個key-value，可以設置map.put(key,null);
循環到字元串的長度為需要的長度。
具體一種方法的代碼：
import java.util.HashMap;
import java.util.Map;
public class RandomStr {
public static void main(String[] args) {
for(int i=0; i< 10; i++){//測試10次產生隨機不重復字元串
generateRandomStr(5);
}
}
/**
* 產生不重復的隨機字元串
* @param len 生成字元串的長度
* @return
*/
public static String generateRandomStr(int len){
String strRange = "";//字元串范圍，根據自己的需求確定
Map<String, String> tmp = new HashMap<String, String>();
for(int i=0; i<strRange.length(); i++){
tmp.put(i+"",strRange.charAt(i)+"");
}
StringBuffer result=new StringBuffer();
for(int i=0; i<len; i++){
String key = (int)(Math.random()*(strRange.length()-i))+"";
result.append(tmp.get(key));
tmp.remove(key);
tmp.put(key, tmp.get((strRange.length()-i-1)+""));//拿最後一個字元填充刪除的位置key-value
}
System.out.println(result);
return result.toString();
}
}
❹ Java如何生成隨機字元串
import java.util.Random;
public class Stat {
public static void main(String[] args) {
// Math.random() 獲取0～1之間的double類型數值
int num = (int)(Math.random()*100); // 獲取0～100之間的整數
System.out.println(num);
System.out.println(getRandomString(12));
}
// 獲取隨機字元串
public static String getRandomString(int length) { // length 字元串長度
StringBuffer buffer = new StringBuffer("");
StringBuffer sb = new StringBuffer();
Random r = new Random();
int range = buffer.length();
for (int i = 0; i < length; i ++) {
sb.append(buffer.charAt(r.nextInt(range)));
}
return sb.toString();
}
}
❺ 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("");
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("");此段字元串代表要出現的字元還可以是其他字元
如：- + = * 。.等等
❻ java實現輸出指定長度的隨機字元（大小寫字母和數字）遇到問題
程序輸出錯誤的原因(見圖)
❼ java中如何產生一個16位數字組成的隨機字元串謝謝各位了
方法如下：
Random ran=new random();
boolean flag=true;
while(flag){
int a=ran.nextInt(99999999);
int b=ran.nextInt(99999999);
long c=a*100000000L+b;
if(c>1000000000000000L&&c<9999999999999999L){
flag=false;
c1=c;
String num=String.valueOf(c1);
}
｝
❽ 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 = ("" +
"").toCharArray();
//numbersAndLetters = ("").toCharArray();
}
char [] randBuffer = new char[length];
for (int i=0; i<randBuffer.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。
❾ java如何定義一個以字母開頭的隨機字元串
需要創建生成器的實例，我們可以使用RandomStringGenerator.Builder()類build()方法。生成器類還可以幫助我們配置生成器的屬性。在調用build()方法之前，我們可以使用以下方法設置構建器的屬性:withinRange()指定在生成的字元串中允許的最小和最大代碼點。filteredBy()將生成的字元串中的字元限制為與至少提供的謂詞之一匹配的字元。這樣即可將java定義一個以字母開頭的隨機字元串。