在 Java 中生成给定大小的随机字符串
原文:https://www . geesforgeks . org/generate-random-string-of-size-in-Java/
假设大小为 n，任务是生成一个随机的字母数字字符串。
以下是生成给定大小的随机字母数字字符串的各种方法:
先决条件:用 Java 生成随机数
-
Method 1: Using Math.random()
这里函数 GetalHanumeRichString(n)生成一个长度为字符串的随机数。这个数字是一个字符的索引，这个字符附加在临时局部变量 sb 中。最后某人回来了。
``` // Java program generate a random AlphaNumeric String // using Math.random() method
public class RandomString {
// function to generate a random string of length n static String getAlphaNumericString(int n) {
// chose a Character random from this String String AlphaNumericString = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789" + "abcdefghijklmnopqrstuvxyz";
// create StringBuffer size of AlphaNumericString StringBuilder sb = new StringBuilder(n);
for (int i = 0; i < n; i++) {
// generate a random number between // 0 to AlphaNumericString variable length int index = (int)(AlphaNumericString.length() * Math.random());
// add Character one by one in end of sb sb.append(AlphaNumericString .charAt(index)); }
return sb.toString(); }
public static void main(String[] args) {
// Get the size n int n = 20;
// Get and display the alphanumeric string System.out.println(RandomString .getAlphaNumericString(n)); } } ```
Output:
``` kU9vRVm9T1lFMbi3duO1
```
方法二:使用字符集
使用 java.nio.charset 包中的 Charset 随机生成 20 个字符长的字母数字字符串。
- 首先取 0 到 256 之间的字符并遍历。
- 检查字符是字母还是数字。
- 如果是，那么在字符串的末尾添加
- 返回字符串
下面是上述方法的实现:
``` // Java program generate a random AlphaNumeric String // using CharSet method
import java.util.; import java.nio.charset.;
class RandomString {
static String getAlphaNumericString(int n) {
// length is bounded by 256 Character byte[] array = new byte[256]; new Random().nextBytes(array);
String randomString = new String(array, Charset.forName("UTF-8"));
// Create a StringBuffer to store the result StringBuffer r = new StringBuffer();
// Append first 20 alphanumeric characters // from the generated random String into the result for (int k = 0; k < randomString.length(); k++) {
char ch = randomString.charAt(k);
if (((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9')) && (n > 0)) {
r.append(ch); n--; } }
// return the resultant string return r.toString(); }
public static void main(String[] args) { // size of random alphanumeric string int n = 20;
// Get and display the alphanumeric string System.out.println(getAlphaNumericString(n)); } } ```
Output:
``` jj06CyZKfSBZQHM6KAUd
```
-
Method 3: Using Regular Expressions
- 首先取 0 到 256 之间的字符。
- 除去除 0-9、a-z 和 A-Z 以外所有字符
- 随机选择一个字符
- 在末尾添加我们需要的变量
下面是上述方法的实现:
``` // Java program generate a random AlphaNumeric String // using Regular Expressions method
import java.util.; import java.nio.charset.;
class RandomString {
static String getAlphaNumericString(int n) {
// length is bounded by 256 Character byte[] array = new byte[256]; new Random().nextBytes(array);
String randomString = new String(array, Charset.forName("UTF-8"));
// Create a StringBuffer to store the result StringBuffer r = new StringBuffer();
// remove all spacial char String AlphaNumericString = randomString .replaceAll("[^A-Za-z0-9]", "");
// Append first 20 alphanumeric characters // from the generated random String into the result for (int k = 0; k < AlphaNumericString.length(); k++) {
if (Character.isLetter(AlphaNumericString.charAt(k)) && (n > 0) || Character.isDigit(AlphaNumericString.charAt(k)) && (n > 0)) {
r.append(AlphaNumericString.charAt(k)); n--; } }
// return the resultant string return r.toString(); }
public static void main(String[] args) { // size of random alphanumeric string int n = 20;
// Get and display the alphanumeric string System.out.println(getAlphaNumericString(n)); } } ```
Output:
``` 4J8pirLzX6oIF0IIIaUU
```
-
Method 4: Generating random String of UpperCaseLetter/LowerCaseLetter/Numbers
当字母数字字符串中需要一些特定的字符时，例如只有大写字母或小写字母或数字，请使用此方法。以下示例生成一个随机的大小为 n 的小写字母字符串。
下面是上述方法的实现:
``` // Java program generate a random // UpperCase or LowerCase or Number String
import java.util.*;
public class GFG {
static String getAlphaNumericString(int n) {
// lower limit for LowerCase Letters int lowerLimit = 97;
// lower limit for LowerCase Letters int upperLimit = 122;
Random random = new Random();
// Create a StringBuffer to store the result StringBuffer r = new StringBuffer(n);
for (int i = 0; i < n; i++) {
// take a random value between 97 and 122 int nextRandomChar = lowerLimit + (int)(random.nextFloat() * (upperLimit - lowerLimit + 1));
// append a character at the end of bs r.append((char)nextRandomChar); }
// return the resultant string return r.toString(); }
public static void main(String[] args) { // size of random alphanumeric string int n = 20;
// Get and display the alphanumeric string System.out.println(getAlphaNumericString(n)); } } ```
Output:
``` qbhalyuzrenuwgvqidno
```
版权属于：月萌API www.moonapi.com，转载请注明出处
