سلام من یه response از یه ادرسی دریافت میکنم 

مشکل اینجاست مثلا مثل کد پایین یه سری از id‌ها فیلد Album دارن ولی یسری دیگه ندارن 

"id": 100586,
      "title": "Nima Masiha - "Payane Harfat"",
      "explicit": false,
      "link": "https://host2.media-rj.com/media/mp3/mp3-256/100586-c4f8f2a8b0ab46c.mp3",
      "photo": "https://assets.rjassets.com/static/mp3/nima-masiha-payane-harfat/53f262f2a744c95.jpg",
      "thumbnail": "https://assets.rjassets.com/static/mp3/nima-masiha-payane-harfat/53f262f2a744c95-thumb.jpg",
      "plays": "13,985",
      "artist": "Nima Masiha",
      "song": "Payane Harfat",
      "photo_240": "https://assets.rjassets.com/static/mp3/nima-masiha-payane-harfat/53f262f2a744c95-photo_240x180.jpg",
      "likes": "59",
      "dislikes": "0",
      "downloads": "13,985",
      "photo_player": "https://assets.rjassets.com/static/mp3/nima-masiha-payane-harfat/0d94a4933725f08-player.jpg",
      "permlink": "Nima-Masiha-Payane-Harfat",
      "share_link": "https://rjapp.app/m/4qL514Nl",
      "created_at": "2021-09-18T11:45:50-04:00",
      "type": "mp3",
      "duration": 256.496,
      "hls_link": "https://host2.media-rj.com/media/mp3/mp3-hls/100586-c4f8f2a8b0ab46c/playlist.m3u8",
      "lq_link": "https://host2.media-rj.com/media/mp3/aac-128/100586-c4f8f2a8b0ab46c.m4a",
      "hq_link": "https://host2.media-rj.com/media/mp3/aac-256/100586-c4f8f2a8b0ab46c.m4a",
      "lq_hls": "https://host2.media-rj.com/media/mp3/mp3-hls/100586-c4f8f2a8b0ab46c/file-96k.m3u8",
      "hq_hls": "https://host2.media-rj.com/media/mp3/mp3-hls/100586-c4f8f2a8b0ab46c/playlist.m3u8",
      "lufs": -5.9,
      "artist_tags": [
        "Nima Masiha"
      ],
      "bg_colors": [
        "#c19b8f",
        "#976453"
      ]

"id": 100622,
      "title": "Arman Miladi & Amin Tijay, & Young Sudden - "Gangsta"",
      "explicit": false,
      "link": "https://host2.media-rj.com/media/mp3/mp3-256/100622-ba2f07903aabf74.mp3",
      "photo": "https://assets.rjassets.com/static/mp3/arman-miladi-amin-tijay-young-sudden-gangsta/b2a6cfac0d2ae28.jpg",
      "thumbnail": "https://assets.rjassets.com/static/mp3/arman-miladi-amin-tijay-young-sudden-gangsta/b2a6cfac0d2ae28-thumb.jpg",
      "plays": "113,477",
      "artist": "Arman Miladi & Amin Tijay, & Young Sudden",
      "song": "Gangsta",
      "photo_240": "https://assets.rjassets.com/static/mp3/arman-miladi-amin-tijay-young-sudden-gangsta/b2a6cfac0d2ae28-photo_240x180.jpg",
      "likes": "262",
      "dislikes": "2",
      "downloads": "113,477",
      "photo_player": "https://assets.rjassets.com/static/mp3/arman-miladi-amin-tijay-young-sudden-gangsta/e7cdced05eec6ab-player.jpg",
      "permlink": "Arman-Miladi-Amin-Tijay-Young-Sudden-Gangsta",
      "share_link": "https://rjapp.app/m/ZEwRZwrv",
      "created_at": "2021-09-20T06:24:46-04:00",
      "type": "mp3",
      "duration": 239.073,
      "hls_link": "https://host2.media-rj.com/media/mp3/mp3-hls/100622-ba2f07903aabf74/playlist.m3u8",
      "lq_link": "https://host2.media-rj.com/media/mp3/aac-128/100622-ba2f07903aabf74.m4a",
      "hq_link": "https://host2.media-rj.com/media/mp3/aac-256/100622-ba2f07903aabf74.m4a",
      "lq_hls": "https://host2.media-rj.com/media/mp3/mp3-hls/100622-ba2f07903aabf74/file-96k.m3u8",
      "hq_hls": "https://host2.media-rj.com/media/mp3/mp3-hls/100622-ba2f07903aabf74/playlist.m3u8",
      "lufs": -9.1,
      "album": {
        "id": 2328,
        "album": "El Quatro",
        "artist": "Arman Miladi",
        "track": 2,
        "share_link": "https://rjapp.app/ma/KwEoQGpV"
      },
      "artist_tags": [
        "Arman Miladi & Amin Tijay, & Young Sudden"
      ],
      "bg_colors": [
        "#e63629",
        "#971b12"
      ]

الان من چجوری باید این json رو به کلاس جاوا تبدیل کنم از کد زیر استاده کردم ولی جواب نداد چون یسری از ایدی‌ها album ندارن 

public int id;
        public String title;
        public boolean explicit;
        public String link;
        public String photo;
        public String thumbnail;
        public String plays;
        public String artist;
        public String song;
        public String photo_240;
        public String likes;
        public String dislikes;
        public String downloads;
        public String photo_player;
        public String permlink;
        public String share_link;
        public String created_at;
        public String type;
        public double duration;
        public String hls_link;
        public String lq_link;
        public String hq_link;
        public String lq_hls;
        public String hq_hls;
        public double lufs;
        public List<String> artist_tags;
        public List<String> bg_colors;
        public Album album;