Java-随机字符串生成方式

转自：https://blog.csdn.net/feifeixuanxuan_java/article/details/47991701

/**
* 各种随机字符串生成的方法
*
* @author Administrator
*
*/
public class RandomString {
public static final String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static final String LETTERCHAR = "abcdefghijkllmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static final String NUMBERCHAR = "0123456789";
/**
* 返回一个定长的随机字符串(包含大小写字母、数字)
*
* @param length
* 随机字符串长度
* @return 随机字符串
*/
public static String generateString(int length) {
StringBuffer sb = new StringBuffer();
Random random = new Random();
for (int i = 0; i < length; i++) {
sb.append(ALLCHAR.charAt(random.nextInt(ALLCHAR.length())));
}
return sb.toString();
}
/**
* 返回一个定长的随机纯字母字符串(只包含大小写字母)
*
* @param length
* 随机字符串长度
* @return 随机字符串
*/
public static String generateUpperLowerString(int length) {
StringBuffer sb = new StringBuffer();
Random random = new Random();
for (int i = 0; i < length; i++) {
sb.append(LETTERCHAR.charAt(random.nextInt(LETTERCHAR.length())));
}
return sb.toString();
}
/**
* 返回一个定长的随机纯小写字母字符串(只包含小写字母)
*
* @param length
* 随机字符串长度
* @return 随机字符串
*/
public static String generateLowerString(int length) {
return generateUpperLowerString(length).toLowerCase();
}
/**
* 返回一个定长的随机纯大写字母字符串(只包含大写字母)
*
* @param length
* 随机字符串长度
* @return 随机字符串
*/
public static String generateUpperString(int length) {
return generateUpperLowerString(length).toUpperCase();
}
/**
* 生成一个定长的纯0字符串
*
* @param length
* 字符串长度
* @return 纯0字符串
*/
public static String generateZeroString(int length) {
StringBuffer sb = new StringBuffer();
for (int i = 0; i < length; i++) {
sb.append('0');
}
return sb.toString();
}
/**
* 根据数字生成一个定长的字符串，长度不够前面补0
*
* @param num
* 数字
* @param fixdlenth
* 字符串长度
* @return 定长的字符串
*/
public static String generateFixdLengthString(long num, int fixedlenth) {
StringBuffer sb = new StringBuffer();
String strNum = String.valueOf(num);
if (fixedlenth - strNum.length() >= 0) {
sb.append(generateZeroString(fixedlenth - strNum.length()));
} else {
throw new RuntimeException("将数字" + num + "转化为长度为" + fixedlenth
+ "的字符串发生异常！");
}
sb.append(strNum);
return sb.toString();
}
/**
* 每次生成的len位数都不相同(仅限于整型数组的每个元素都0-9这十个基本数字，且len的值还不能大于数组的长度)
*
* @param param
* @return 定长的数字
*/
public static int generateDifferentNum(int[] param, int len) {
Random rand = new Random();
for (int i = param.length; i > 1; i--) {
int index = rand.nextInt(i);
int tmp = param[index];
param[index] = param[i - 1];
param[i - 1] = tmp;
}
int result = 0;
for (int i = 0; i < len; i++) {
result = result * 10 + param[i];
}
return result;
}
}