Job Assignment Java

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package jobassignment;

import java.util.ArrayList;

/**
 *
 * @author Whoami
 */
public class JobAssignment {


    public ArrayList<String> performPermutations(String s){
        ArrayList<String> arrayList;
        arrayList = new ArrayList<>();
        if(s == null){
            return null;
        }else if(s.length() == 0){
            arrayList.add("");
            return arrayList;
        }else{
            for(int i = 0; i< s.length(); i++){
                ArrayList<String> remaining = performPermutations(s.substring(0,i)+ s.substring(i + 1));
                for(int j = 0; j < remaining.size(); j++){
                    arrayList.add(s.charAt(i) + remaining.get(j));
                }
            }
            return arrayList;
        }
    }

    public static int[] konversi(String a){
        int[]ind=new int[a.length()];
        for(int i = 0; i < a.length(); i++){
            switch (a.charAt(i)) {
                case '1':
                    ind[i]=1;
                    break;
                case '2':
                    ind[i]=2;
                    break;
                case '3':
                    ind[i]=3;
                    break;
                case '4':
                    ind[i]=4;
                    break;
                default:
                    ind[i]=5;
                    break;
            }
        }
        return ind;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        int [][]data = {{5,7,4,3},{10,9,7,6},{2,4,5,3},{3,1,2,3}};
        JobAssignment p = new JobAssignment();
        ArrayList<String> arr = p.performPermutations("1234");

        int kecil = 1000;
        String benar = arr.get(0);
        for(int i = 0; i < arr.size(); i++){
            String a = arr.get(i);
            int []ind = konversi(a);
            int nData = (ind.length);
            int total = 0;

            for(int j=0;j<nData;j++){
                int z=ind[j]-1;
                total=total+data[z][j];
            }

            if(kecil>total){
                kecil = total;
                benar = a;
            }

        }
        System.out.println("Urutan pekerja = " + benar);
        System.out.println("Cost total pekerjaan= " + kecil);

    }

}