Using replaceAll on a string doesn't work

I tried to solve this task, but I failed because return won’t work.
I’m new to java and hope you can help me.

The task is to delete every x in a string, but not the first and last one.

public class Main {
    
     public static String stringX(String s) { 
         boolean start = s.startsWith("x");
         boolean end = s.endsWith("x");
         int end1 = s.length() - 1;
         if (start & end) { 
                s.substring(1, end1).replace("x", "");
                
            } else {
                s.replaceAll("x", "");
            }
        return s;
    }

    public static void main(String[] args) {
        String result = stringX("xxHix");
        System.out.println(result); // => xHix

        System.out.println(stringX("abxxxcd")); // => abcd
        System.out.println(stringX("xabxxxcdx")); // => xabcdx
    }
}

>Solution :

The operation you’re using doesn’t modify s inplace, you need to retrieve the updated string

s = s.substring(1, end1).replace("x", "");
s = s.replaceAll("x", "");

But the substring + replace won’t work as it removes the first and last char too

You’d better replace all x, then add where it’s needed

public static String stringX(String s) { 
     String trimmed = s.replace("x", "");
     if(s.startsWith("x"))
         trimmed = "x" + trimmed;
     if(s.endsWith("x"))
         trimmed += "x";
    return trimmed;
}

Or use a nice regex (?<!^)x(?!$)

• (?<!^)x is a Negative Lookbehind and ensure that there is no start of string before the x : x is not first char

• x(?!$) is a Negative Lookahead and ensure that there is no end of string after the x : x is not a last char

public static String stringX(String s) { 
    return s.replaceAll("(?<!^)x(?!$)", "");
}