ISC 2020 solved program (Object passing as an argument)

import java.util.*;
class Mix
{   scanner sc=new scanner(system.in);
    int len;
    string wrd;
    Mix()
    {
        len=0;
        wrd="";
    }
    void feedword()
    {
        system.out.println("enter a word");
        wrd=sc.next();  
    }
    void mix_word(mix a, mix b)
    {
        string str1="";
        int len1=a.wrd.length();
        int len2= b.wrd.length();
        if(len1>len2)
            str1=a.wrd;  
        else
            str1=b.wrd;
        int len=math.min(len1,len2);
        for(int i=0;i<len;i++)
        {
            this.wrd+= a.wrd.charat(i);     
            this.wrd+=b.wrd.charat(i);
        }
        for(int i=len;i<str1.length();i++)
            this.wrd+=str1.charat(i);  
    }
    void display()
    {
        system.out.println("the word is "+ wrd);
    }
    public static void main()
    {
        Mix a =new Mix();
        a.feedword();
        Mix b =new Mix();
        b.feedword();
        Mix obj =new Mix();
        obj.mix_word(a, b);
        obj.display();                
    }
}