错误：类型不兼容：对象无法转换为char

Question

I've implemented a method to reverse a String using stack as ArrayList, but an error says error: incompatible types: Object cannot be converted to char . How can I fix it?

Here is the stack class:

public static class stackl extends ArrayList {
    public boolean isEmptyS() {
        return isEmpty();
    }

    public void push(Object el) {
        add(0, el);
    }

    public Object pop() {
        return remove(0);
    }
}

And here is my method:

public static void reverse(String s) {
    stackl s1 = new stackl();
    for (int j = 0; j < s.length(); j++) {
        char ch = s.charAt(j);
        s1.push(ch);
    }

    while (!s1.isEmpty()) {
        char ch = s1.pop();
        System.out.println(ch);
    }
}

Answer 1

You can convert a char to a Character with auto-boxing. Try

Character ch = s.charAt(j);

Also, it would make sense to have a generic stack just like the built in Stack (have a look at the code for Stack as an example)