请问java如何去掉字符串中的数字和特殊符号？

比如输入adadad！@#@112

输入得是adadad

求大神讲解

package test;

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        String str;
        int i;
        str = reader.nextLine();//输入整行字符串
        char b[] = str.toCharArray();//转换成字符数组
        for (i = 0; i < b.length; i++) {
            if ((b[i] >= 'a' && b[i] <= 'z') || (b[i] >= 'A' && b[i] <= 'Z')) {
                System.out.print(b[i]);
            }
        }
    }
}

望采纳 

"adadad！@#@112".replaceAll("[需要删除的字符/正则]","");