I got the wrong result from the Math.pow() while trying to figure out Armstrong

public class ArmStrongNumber {
    public static void main(String[] args) {
        for(int i = 0; i < 10000; i++){    
            String st = String.valueOf(i);
            int digitNumber = st.length();
            char[] ch = st.toCharArray();
            int result = 0;
            for(int j = 0; j < digitNumber; j++){
                result += Math.pow(ch[j], digitNumber);
            }
            if(i == result){
                System.out.println(i);
            }  
        } 
    } 
}

I have tried many time. When I checked for the result, it’s all incorrect calculation. I think the problem is the Math pow?