the below code input o1ps will return oops but o2ps should return ooops is there any way we can execute o2ps has ooops

package adc;
import java.util.*;
public class bca {
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter the sentence to decrypt");
String s=sc.nextLine();
char[] ans = s.toCharArray();
int len=s.length();
char[] sol= new char[len];
System.out.println("len="+s.length());
for(int i=0;i<len;i++) {
    int j=i;
    if(ans[i]=='1') {
        sol[i]=ans[i-1];
    }
    else if(ans[i]=='2') {
        sol[i]=ans[i-1];
        sol[i+1]=ans[i-1];
        
        
    }
    else {
        sol[i]=ans[i];
    }
    System.out.print(sol[i]);
    }
  sc.close();
    
  }
  }

new here learning java tring to get some help here thank you.

Enter the sentence to decrypt Input:o1ps o2ps output:len=9 oops oopsis it possible to make o2ps has ooops

You need different counters for the input string and the output string, however, as you don't know in advance the length of the output string, you can use a StringBuilder:

    char[] ans = s.toCharArray();
    StringBuilder out = new StringBuilder();
    System.out.println("len=" + s.length());
    for (int i = 0; i < ans.length; i++) {
        if (i > 0 && ans[i] >= '0' && ans[i] <= '9') {
            char prev = ans[i-1];
            int count = ans[i] - '0';
            for (int j = 0; j < count; ++j) {
                out.append(prev);
            }
        } else {
            out.append(ans[i]);
        }
    }
    System.out.println("output=" + out);

UPDATE:

To also reverse words:

    char[] ans = s.toCharArray();
    List<String> words = new ArrayList<>();
    StringBuilder out = new StringBuilder();
    System.out.println("len=" + s.length());
    for (int i = 0; i < ans.length; i++) {
        if (ans[i] == ' ') {
            if (out.length() > 0) {
                words.add(out.toString());
                out.setLength(0);
            }
        } else if (i > 0 && ans[i] >= '0' && ans[i] <= '9') {
            char prev = ans[i-1];
            int count = ans[i] - '0';
            for (int j = 0; j < count; ++j) {
                out.append(prev);
            }
        } else {
            out.append(ans[i]);
        }
    }
    if (out.length() > 0) {
        words.add(out.toString());
    }
    Collections.reverse(words);
    String output = words.stream().collect(Collectors.joining(" "));
    System.out.println("output=" + output);