Find the occurence of each character in the given String ?

import java.util.*;

public class Main {
static void rev(String a)
{
int n=a.length();
int arr[]=new int[26];
for(int i=0;i<n;i++)
arr[a.charAt(i)-97]++;
for(int i=0;i<n;i++)
if(arr[a.charAt(i)-97]>0)
{
System.out.println(a.charAt(i)+" - "+arr[a.charAt(i)-97]);
arr[a.charAt(i)-97]=0;
}
}
public static void main(String[] args) {
Scanner s=new Scanner(System.in);
String a=s.nextLine();
rev(a);
}
}