com.google.gson.JsonSyntaxException:Expected STRING but was BEGIN_ARRAY

Kindly help me to get the subnodes list inside bom attributes

JSON file

[  
 {  
  "subConfigId":"bac",
  "totalPrice":"634.00",
  "bom":{  
     "ucid":"ucid",
     "type":"RootNode",
     "attributes":{  
        "visible":true,
        "price_status":"SUCCESS"
     },
     "subnodes":[  
        {  
           "description":"Enterprise Shock Rack",
           "ucid":"ucid"
        },
        {  
           "description":"SVC",
           "ucid":"ucid"
        }
     ]
  },
  "breakdown":{  
     "SV":550.0,
     "HW":6084.0
  },
  "currency":"USD"
 }
]

GsonNodes.java

 import java.io.FileReader;
 import java.io.IOException;
 import java.util.Iterator;
 import com.google.gson.Gson;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonParser;

  public class GsonNodes {
  public static void main(String[] args) throws IOException {   

    try{                 
     JsonElement je = new JsonParser().parse(new FileReader(
             "C:/Desktop/json.txt"));
     JsonArray ja = je.getAsJsonArray();
     Iterator itr = ja.iterator();

     while(itr.hasNext()){
         JsonElement je1 = (JsonElement) itr.next();
         Gson gson = new Gson();
         Details details = gson.fromJson(je1, Details.class);          

         System.out.println(details.getSubConfigId());
         System.out.println(details.getCurrency());
         System.out.println(details.getBreakdown());
         System.out.println(details.getTotalPrice());
         System.out.println(details.getBom().getUcid());         

     }
  } catch (Exception e) {
  e.printStackTrace();
  }
}
}

Details.java POJO

    import java.io.Serializable;
    import java.util.Map;
    public class Details implements Serializable{

        private String subConfigId;
        private String totalPrice;
        private Bom bom;     
        private String currency;
        private Map<String, String> breakdown;

        public String getSubConfigId() {
            return subConfigId;
        }
        public void setSubConfigId(String subConfigId) {
            this.subConfigId = subConfigId;
        }
        public String getTotalPrice() {
            return totalPrice;
        }
        public void setTotalPrice(String totalPrice) {
            this.totalPrice = totalPrice;
        }
        public Bom getBom() {
            return bom;
        }
        public void setBom(Bom bom) {
            this.bom = bom;
        }
        public String getCurrency() {
            return currency;
        }
        public void setCurrency(String currency) {
            this.currency = currency;
        }
        public Map<String, String> getBreakdown() {
            return breakdown;
        }
        public void setBreakdown(Map<String, String> breakdown) {
            this.breakdown = breakdown;
        }
    }

Bom.java

    import java.io.Serializable;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;

    public class Bom implements Serializable{

        private String ucid;
        private String type;
        private Map<String, String> attributes;
        private List<Subnodes> subnodes = new ArrayList<Subnodes>();  

        public String getUcid() {
            return ucid;
        }
        public void setUcid(String ucid) {
            this.ucid = ucid;
        }
        public String getType() {
            return type;
        }
        public void setType(String type) {
            this.type = type;
        }
        public Map<String, String> getAttributes() {
            return attributes;
        }
        public void setAttributes(Map<String, String> attributes) {
            this.attributes = attributes;
        }   

        @Override
        public String toString(){
            return getUcid() + ", "+getType()+", "+getAttributes();
        }

    }

Subnodes.java

    import java.io.Serializable;
    import java.util.Map;

    public class Subnodes implements Serializable{

        private String description;
        private String ucid;
        private Map<String, String> attributes;

        public String getDescription() {
            return description;
        }
        public void setDescription(String description) {
            this.description = description;
        }
        public String getUcid() {
            return ucid;
        }
        public void setUcid(String ucid) {
            this.ucid = ucid;
        }
        public Map<String, String> getAttributes() {
            return attributes;
        }
        public void setAttributes(Map<String, String> attributes) {
            this.attributes = attributes;
        }   
    }

I am getting an error , when i try to get the "subnodes" I added the following code in the class

  private List<Subnodes> subnodes = new ArrayList<Subnodes>();

then i am getting the error "Expected STRING but was BEGIN_ARRAY"

kindly help me that how can i get the "subnodes" list