class Example {
    public static void main(String[] args) throws Exception {
        String s = "admin\0\0\0\0\0\0\0";
 
        System.out.println(s);
        System.out.println(s.length());
 
        s = s.replaceAll(new String(new byte[] {0}, "UTF-8"), "");
        System.out.println(s.length());
    }
 
    static {
        Thread.currentThread()
            .setUncaughtExceptionHandler((t, e) ->
                e.printStackTrace(System.out));
    }
}

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