java 隨機數 優惠碼 生成 隨機字串

package test;
import java.util.HashSet;
import java.util.Random;  
import java.util.Set;
public class RandomUtil {
        public static final String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";  
        public static final String LETTERCHAR = "abcdefghijkllmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";  
        public static final String NUMBERCHAR = "0123456789";  

          
        /** 
         * 返回一個定長的隨機字符串(數字) 
         *  
         * @param length 
         *            隨機字符串長度 
         * @return 隨機字符串 
         */  
        public static String generateOnlyNumber(int length) {  
            StringBuffer sb = new StringBuffer();  
            Random random = new Random();  
            for (int i = 0; i < length; i++) {  
                sb.append(NUMBERCHAR.charAt(random.nextInt(NUMBERCHAR.length())));  
            }  
            return sb.toString();  
        }  

        
        /** 
         * 返回一個定長的隨機字符串(只包含大小寫字母、數字) 
         *  
         * @param length 
         *            隨機字符串長度 
         * @return 隨機字符串 
         */  
        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();  
        }  
      
        /** 
         * 返回一個定長的隨機純字母字符串(只包含大小寫字母) 
         *  
         * @param length 
         *            隨機字符串長度 
         * @return 隨機字符串 
         */  
        public static String generateMixString(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();  
        }  
      
        /** 
         * 返回一個定長的隨機純大寫字母字符串(只包含大小寫字母) 
         *  
         * @param length 
         *            隨機字符串長度 
         * @return 隨機字符串 
         */  
        public static String generateLowerString(int length) {  
            return generateMixString(length).toLowerCase();  
        }  
      
        /** 
         * 返回一個定長的隨機純小寫字母字符串(只包含大小寫字母) 
         *  
         * @param length 
         *            隨機字符串長度 
         * @return 隨機字符串 
         */  
        public static String generateUpperString(int length) {  
            return generateMixString(length).toUpperCase();  
        }  
      
        /** 
         * 生成一個定長的純0字符串 
         *  
         * @param length 
         *            字符串長度 
         * @return 純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();  
        }  
      
        /** 
         * 根據數字生成一個定長的字符串，長度不夠前面補0 
         *  
         * @param num 
         *            數字 
         * @param fixdlenth 
         *            字符串長度 
         * @return 定長的字符串 
         */  
        public static String toFixdLengthString(long num, int fixdlenth) {  
            StringBuffer sb = new StringBuffer();  
            String strNum = String.valueOf(num);  
            if (fixdlenth - strNum.length() >= 0) {  
                sb.append(generateZeroString(fixdlenth - strNum.length()));  
            } else {  
                throw new RuntimeException("將數字" + num + "轉化為長度為" + fixdlenth  
                        + "的字符串發生異常！");  
            }  
            sb.append(strNum);  
            return sb.toString();  
        }  
      
        /** 
         * 每次生成的len位數都不相同 
         *  
         * @param param 
         * @return 定長的數字 
         */  
        public static int getNotSimple(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;  
        }  
      
        public static void main(String[] args) {  
            System.out.println("返回一個定長的隨機字符串(只包含大小寫字母、數字):" + generateString(10));  
            System.out  
                    .println("返回一個定長的隨機純字母字符串(只包含大小寫字母):" + generateMixString(10));  
            System.out.println("返回一個定長的隨機純小寫字母字符串(只包含大小寫字母):"  
                    + generateLowerString(10));  
            System.out.println("返回一個定長的隨機純大寫字母字符串(只包含大小寫字母):"  
                    + generateUpperString(10));  
            System.out.println("生成一個定長的純0字符串:" + generateZeroString(10));  
            System.out.println("根據數字生成一個定長的字符串，長度不夠前面補0:"  
                    + toFixdLengthString(123, 10));  
            int[] in = { 1, 2, 3, 4, 5, 6, 7 };  
            System.out.println("每次生成的len位數都不相同:" + getNotSimple(in, 3));  
            
            int i=0;
            Set codes = new HashSet();
            while(codes.size()<10){
                i++;
                codes.add(generateOnlyNumber(10));
            
            }
            System.out.println("返回一個定長的隨機字符串(數字):" +codes.toString() );
            System.out.println("返回一個定長的隨機字符串(數字) 產生次數:" +i );
        }  
}