ADDITIONAL SYSTEM INFORMATION :
windows10

A DESCRIPTION OF THE PROBLEM :
In java 1.8.0_241 version, treeSet cannot be deduplicated. If the set element exceeds 2, it cannot be deduplicated. It will be possible later. Here is the code

REGRESSION : Last worked in version 8

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
@Data
public class AreaMapEntity implements Comparable<AreaMapEntity> {

    // 国家 代码
    private String countrySimpleCode;
    // 国家英文
    private String countryEnglishName;
    // 国家总和
    private long countryHotNumber = 0L;

    // 国家下面的城市
    private Set<CityMapEntity> citys = new HashSet<>();

    public static class CityMapEntity implements Comparable<CityMapEntity> {
        private String citySimpleCode;
        private String cityEnglishName;
        private long cityUserHotNumber = 0L;

        public CityMapEntity() {
        }

        public CityMapEntity(String citySimpleCode, String cityEnglishName, long cityUserHotNumber) {
            this.citySimpleCode = citySimpleCode;
            this.cityEnglishName = cityEnglishName;
            this.cityUserHotNumber = cityUserHotNumber;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            CityMapEntity that = (CityMapEntity) o;
            return Objects.equals(cityEnglishName, that.cityEnglishName);
        }

        @Override
        public int hashCode() {
            return Objects.hash(cityEnglishName);
        }

        @Override
        public int compareTo(CityMapEntity o) {
            if (this.getCityEnglishName().equals(o.getCityEnglishName())) {
                return 0;
            } else {
                if (this.getCityUserHotNumber() <= o.getCityUserHotNumber()) {
                    return 1;
                } else {
                    return -1;
                }
            }

            /*if (this.getCityUserHotNumber() <= o.getCityUserHotNumber()) {
                return 1;
            } else {
                return -1;
            }*/
        }

        public String getCitySimpleCode() {
            return citySimpleCode;
        }

        public void setCitySimpleCode(String citySimpleCode) {
            this.citySimpleCode = citySimpleCode;
        }

        public String getCityEnglishName() {
            return cityEnglishName;
        }

        public void setCityEnglishName(String cityEnglishName) {
            this.cityEnglishName = cityEnglishName;
        }

        public long getCityUserHotNumber() {
            return cityUserHotNumber;
        }

        public void setCityUserHotNumber(long cityUserHotNumber) {
            this.cityUserHotNumber = cityUserHotNumber;
        }
    }


    @Override
    public int compareTo(AreaMapEntity areaMapEntity) {
        if (this.getCountrySimpleCode().equals(areaMapEntity.getCountrySimpleCode())) {
            return 0;
        } else {
            if (this.getCountryHotNumber() <= areaMapEntity.getCountryHotNumber()) {
                return 1;
            } else {
                return -1;
            }
        }
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        AreaMapEntity that = (AreaMapEntity) o;
        return Objects.equals(countrySimpleCode, that.countrySimpleCode);
    }

    @Override
    public int hashCode() {
        return Objects.hash(countrySimpleCode);
    }
}
public static void main(String[] args) throws Exception {
        Set<AreaMapEntity> res = new TreeSet<>();

        AreaMapEntity a = new AreaMapEntity();
        a.setCountrySimpleCode("MM");
        a.setCountryEnglishName("Myanmar");

        AreaMapEntity b = new AreaMapEntity();
        b.setCountrySimpleCode("MY");
        b.setCountryEnglishName("Malaysia");

        AreaMapEntity c = new AreaMapEntity();
        c.setCountrySimpleCode("TH");
        c.setCountryEnglishName("Thailand");

        AreaMapEntity d = new AreaMapEntity();
        d.setCountrySimpleCode("SA");
        d.setCountryEnglishName("Saudi Arabia");


        AreaMapEntity e = new AreaMapEntity();
        e.setCountrySimpleCode("MM");
        e.setCountryEnglishName("Myanmar");


        res.add(a);
        res.add(a);
        res.add(a);
        res.add(b);
        res.add(c);
        res.add(d);
        res.add(e);

        System.out.println(res);
    }

ACTUAL -
The expected result is that it can be deduplicated but cannot be deduplicated in practice. The variable e is saved in, and there is no need to save the variable e.

---------- BEGIN SOURCE ----------
@Data
public class AreaMapEntity implements Comparable<AreaMapEntity> {

    // 国家 代码
    private String countrySimpleCode;
    // 国家英文
    private String countryEnglishName;
    // 国家总和
    private long countryHotNumber = 0L;

    // 国家下面的城市
    private Set<CityMapEntity> citys = new HashSet<>();

    public static class CityMapEntity implements Comparable<CityMapEntity> {
        private String citySimpleCode;
        private String cityEnglishName;
        private long cityUserHotNumber = 0L;

        public CityMapEntity() {
        }

        public CityMapEntity(String citySimpleCode, String cityEnglishName, long cityUserHotNumber) {
            this.citySimpleCode = citySimpleCode;
            this.cityEnglishName = cityEnglishName;
            this.cityUserHotNumber = cityUserHotNumber;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            CityMapEntity that = (CityMapEntity) o;
            return Objects.equals(cityEnglishName, that.cityEnglishName);
        }

        @Override
        public int hashCode() {
            return Objects.hash(cityEnglishName);
        }

        @Override
        public int compareTo(CityMapEntity o) {
            if (this.getCityEnglishName().equals(o.getCityEnglishName())) {
                return 0;
            } else {
                if (this.getCityUserHotNumber() <= o.getCityUserHotNumber()) {
                    return 1;
                } else {
                    return -1;
                }
            }

            /*if (this.getCityUserHotNumber() <= o.getCityUserHotNumber()) {
                return 1;
            } else {
                return -1;
            }*/
        }

        public String getCitySimpleCode() {
            return citySimpleCode;
        }

        public void setCitySimpleCode(String citySimpleCode) {
            this.citySimpleCode = citySimpleCode;
        }

        public String getCityEnglishName() {
            return cityEnglishName;
        }

        public void setCityEnglishName(String cityEnglishName) {
            this.cityEnglishName = cityEnglishName;
        }

        public long getCityUserHotNumber() {
            return cityUserHotNumber;
        }

        public void setCityUserHotNumber(long cityUserHotNumber) {
            this.cityUserHotNumber = cityUserHotNumber;
        }
    }


    @Override
    public int compareTo(AreaMapEntity areaMapEntity) {
        if (this.getCountrySimpleCode().equals(areaMapEntity.getCountrySimpleCode())) {
            return 0;
        } else {
            if (this.getCountryHotNumber() <= areaMapEntity.getCountryHotNumber()) {
                return 1;
            } else {
                return -1;
            }
        }
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        AreaMapEntity that = (AreaMapEntity) o;
        return Objects.equals(countrySimpleCode, that.countrySimpleCode);
    }

    @Override
    public int hashCode() {
        return Objects.hash(countrySimpleCode);
    }
}
public static void main(String[] args) throws Exception {
        Set<AreaMapEntity> res = new TreeSet<>();

        AreaMapEntity a = new AreaMapEntity();
        a.setCountrySimpleCode("MM");
        a.setCountryEnglishName("Myanmar");

        AreaMapEntity b = new AreaMapEntity();
        b.setCountrySimpleCode("MY");
        b.setCountryEnglishName("Malaysia");

        AreaMapEntity c = new AreaMapEntity();
        c.setCountrySimpleCode("TH");
        c.setCountryEnglishName("Thailand");

        AreaMapEntity d = new AreaMapEntity();
        d.setCountrySimpleCode("SA");
        d.setCountryEnglishName("Saudi Arabia");


        AreaMapEntity e = new AreaMapEntity();
        e.setCountrySimpleCode("MM");
        e.setCountryEnglishName("Myanmar");


        res.add(a);
        res.add(a);
        res.add(a);
        res.add(b);
        res.add(c);
        res.add(d);
        res.add(e);

        System.out.println(res);
    }
---------- END SOURCE ----------

FREQUENCY : always