Java Program to accept any String and show the frequency of every character of the String

The following code is the print the frequency or the total occurrence of the characters in a String entered by the user.
Code:-

import java.util.*;
public class Frequency{
    Scanner scan=new Scanner(System.in);
    String string;
    int occurance=0, count=0, max=0, gap=0, length;
    public void input(){
        try{
            System.out.println("Enter any String to print its Frequency: ");
            string=scan.nextLine();
        }
        catch(Exception e){
            System.out.println("Error Code: "+e);
            System.exit(0);
        }
    }

    public void compute(){
        length=string.length();
        System.out.println("Character\tFrequency");
        for(int i=0; i<length; i++){
            occurance=0;
            count=1;
            for(int j=i-1; j>=0; j--)
                if(string.charAt(j)==string.charAt(i)){
                    occurance=1;
                    break;
            }
            if(occurance==0){
                for(int j= i+1; j<length; j++)
                    if(string.charAt(j)==string.charAt(i))
                        count++;
            }
            System.out.println("    "+string.charAt(i)+"\t\t    "+count);
        }
    }

    public static void main(String[] args){
        Frequency freq=new Frequency();
        freq.input();
        freq.compute();
    }
}

Output:-
Enter any String to print its Frequency:
FREQUENCY
Character   Frequency
    F                 1
    R                 1
    E                 2
    Q                1
    U                1
    E                 1
    N                1
    C                1
    Y                1