java自定义随机数(实例)

import java.util.Random;

/**
 * 
 * @author mengzw
 * @since 3.0 2014-5-22
 */
public class RandomTest {

    
    /**
     * 生成随机字符串
     * 
     * @param length
     *            要生成字符串的长度
     * @param stringType
     *            字符源的类型。0:字母+数字(已把数字中的易混淆字符去除), 1:纯字母, 2:纯数字。默认为字母+数字
     * @param caseType
     *            大小写的类型。0:大小写混合, 1:纯大字, 2:纯小写。默认为纯大写
     * @param specialString
     *            特殊字符 如果需要生成的字符串中包含特殊字符，可把需要添加的特殊字符传进来。该参数为null或""都没关系
     * @return
     */
    public static String getRandomString(int length, int stringType, int caseType, String specialString) {
        String type0 = "abcdefghijkmnopqrstuvwxyz23456789";
        String type1 = "abcdefghijkmnopqrstuvwxyz";
        String type2 = "0123456789";
        String characterStore = "";
        switch (stringType) {
        case 0:
            characterStore = type0;
            break;
        case 1:
            characterStore = type1;
            break;
        case 2:
            characterStore = type2;
            break;
        default:
            characterStore = type0;
            break;
        }
        characterStore += specialString;

        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(characterStore.length());
            char c = characterStore.charAt(number);
            switch (caseType) {
            case 0:
                c = random.nextBoolean() ? Character.toUpperCase(c) : Character.toLowerCase(c);
                break;
            case 1:
                c = Character.toUpperCase(c);
                break;
            case 2:
                c = Character.toLowerCase(c);
                break;
            default:
                c = Character.toUpperCase(c);
                break;
            }
            sb.append(c);
        }
        return sb.toString();
    }
    
    public static void main(String[] args) {
        System.out.println(getRandomString(5,0,0,""));
    }
}