原文：Java随机取字符串的工具类

源代码下载地址：http://www.zuidaima.com/share/1550463479532544.htm

Java 随机取字符串的工具类 可以全部是数字，字符，也可以字符和数字组合的工具类，希望能给大家带来帮助

package com.zuidaima.test;

import java.util.Random;

public class RandomUtils {
	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(只包含大小写字母、数字) 
     * @param length 随机字符串长度 
     * @author www.zuidaima.com
     * @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 
     * @author www.zuidaima.com
     * @return 随机字符串 
     */ 
    public static String generateMixString(int length)
    { 
            StringBuffer sb = new StringBuffer(); 
            Random random = new Random(); 
            for (int i = 0; i < length; i++)
            { 
                    sb.append(ALLCHAR.charAt(random.nextInt(LETTERCHAR.length()))); 
            } 
            return sb.toString(); 
    } 
    /** 
     * 返回一个定长的随机纯大写字母字符串(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 generateLowerString(int length) { 
            return generateMixString(length).toLowerCase(); 
    } 

    /** 
     * 返回一个定长的随机纯小写字母字符串(只包含大小写字母) 
     * 
     * @param length 随机字符串长度 
     * @author www.zuidaima.com
     * @return 随机字符串 
     */ 
    public static String generateUpperString(int length) { 
            return generateMixString(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 
     * @author www.zuidaima.com
     * @return 定长的字符串 
     */ 
    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("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！"); 
            } 
            sb.append(strNum); 
            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 
     * @author www.zuidaima.com
     * @return 定长的字符串 
     */ 
    public static String toFixdLengthString(int 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("将数字" + num + "转化为长度为" + fixdlenth + "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
     * @param param   
     * @return 定长的数字
     */
    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(generateString(10)); 
            System.out.println(generateMixString(10)); 
            System.out.println(generateLowerString(10)); 
            System.out.println(generateUpperString(10)); 
            System.out.println(generateZeroString(10)); 
            System.out.println(toFixdLengthString(123, 10)); 
            System.out.println(toFixdLengthString(123L, 10)); 
            int[] in = {1,2,3,4,5,6,7};
            System.out.println(getNotSimple(in,3));
    } 
}

Java随机取字符串的工具类