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Lỗi biên dịch:

Main.java:13: error: cannot find symbol
        int n = sc.nextInt(chuoi); 
                           ^
  symbol:   variable chuoi
  location: class Main
Main.java:14: error: cannot find symbol
        String chuoi = transform(n);
                       ^
  symbol:   method transform(int)
  location: class Main
Main.java:17: error: cannot find symbol
            for (char c : sequence.toCharArray()) {
                          ^
  symbol:   variable sequence
  location: class Main
Main.java:24: error: cannot find symbol
            sequence = ChuoiMoi.toString();
            ^
  symbol:   variable sequence
  location: class Main
Main.java:28: error: cannot find symbol
        int count = countDoubleZeros(chuoi);
                    ^
  symbol:   method countDoubleZeros(String)
  location: class Main
Main.java:42: error: incompatible types: unexpected return value
        return sequence;
               ^
Main.java:43: error: variable count is already defined in method main(String[])
        int count = 0;
            ^
Main.java:49: error: incompatible types: unexpected return value
        return count;
               ^
8 errors