[Java练习]输入一个字符串，输出其中某个小写字母出现的次数

package com.company;

import java.sql.*;

public class Main
{

public static void main(String[] args) throws ClassNotFoundException, SQLException
{
System.out.println("请输入一个字符串：");
Scanner sc = new Scanner(System.in);
String str = sc.nextLine();

char[] ch = str.toCharArray();
char a1 = 'a';

while (a1<= 'z')
{
int n = 0;

for (int i = 0; i < ch.length; i++)
{

if (a1 == ch[i])
{
n++;
}

}
if(n!=0) System.out.println(a1+": "+n+"个");

a1++;
}
}
}