import java.util.*;
 
class Main{
    public static void main (String args[]){
        String str = "Hello world";
        String str1 = "word";
 
        char []ch = str.toCharArray();
        char []ch1 = str1.toCharArray();
        List<Character> al = new ArrayList();
 
        StringBuilder sb = new StringBuilder();
 
        for (int i=0;i<ch1.length;i++){
            for(int j=0;j<ch.length;j++){
                if (ch1[i] == ch[j]){
                    al.add(ch1[i]);
                    System.out.println("al -- " + al.get(i));
                }
            }
        }
 System.out.println("al" + al.size());
        for (int i=0;i<al.size();i++){
            if(!(str.contains(String.valueOf(al.get(i))))){
                sb = sb.append(String.valueOf(al.get(i)));
            }
        }
        System.out.println(":::" + sb.toString());
    }
}

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