frequency of letters in english java

1public class Frequency   
2{  
3     public static void main(String[] args) {  
4        String str = "picture perfect";  
5        int[] freq = new int[str.length()];  
6        int i, j;  
7          
8        //Converts given string into character array  
9        char string[] = str.toCharArray();  
10          
11        for(i = 0; i <str.length(); i++) {  
12            freq[i] = 1;  
13            for(j = i+1; j <str.length(); j++) {  
14                if(string[i] == string[j]) {  
15                    freq[i]++;             
16                    //Set string[j] to 0 to avoid printing visited character  
17                    string[j] = '0';  
18                }  
19            }  
20        }  
21        //Displays the each character and their corresponding frequency  
22        System.out.println("Characters and their corresponding frequencies");  
23        for(i = 0; i <freq.length; i++) {  
24            if(string[i] != ' ' && string[i] != '0')  
25                System.out.println(string[i] + "-" + freq[i]);  
26        }  
27    }  
28}  

1Map<Character, Long> frequency =
2            str.chars()
3               .mapToObj(c -> (char)c)
4               .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));