JSONArray array =新的JSONArray（string_of_json_array）;

我正在尝试使用GSON和for循环解析Java中的Json arraylist（children）。但是我收到以下错误：

for each not applicable to expression type
required:array or java.lang.iterable
found:String

这是显示此错误的主要Java类

 try {
     br = new BufferedReader(new FileReader("user.json"));
     Tree result = gson.fromJson(br, Tree.class);

    if (result !=null){  
      for (User t : result.getCategory()){  //ERROR IS HERE (squiggly red line)
         System.out.println(t.getId() + "-" + t.getName() + "-" + t.getCategory() + "-" + t.getPercentage());  //ERROR IS ALSO HERE FOR EACH VARIABLES
     }
    }


} catch (FileNotFoundException e) {
    e.printStackTrace();
} finally {
  if (br != null){

      try {
          br.close();
      } catch (IOException e) {
         e.printStackTrace();
      }

  }

这是树类：

    private String category;
@SerializedName("children")
@Expose
private List<Child> children = new ArrayList<Child>();

public String getCategory() {
return category;
}

public void setCategory(String category) {
this.category = category;
}

public List<Child> getChildren() {
return children;
}

public void setChildren(List<Child> children) {
this.children = children;
}

用户类别：

 private String id;
@SerializedName("processed_lang")
@Expose
private String processedLang;
@SerializedName("source")
@Expose
private String source;
@SerializedName("tree")
@Expose
private Tree tree;

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getProcessedLang() {
return processedLang;
}

public void setProcessedLang(String processedLang) {
this.processedLang = processedLang;
}

public String getSource() {
return source;
}

public void setSource(String source) {
this.source = source;
}

public Tree getTree() {
return tree;
}

public void setTree(Tree tree) {
this.tree = tree;
}
    String getName() {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

有人可以让我知道我哪里出错了，如果你们想看看json代码，请让我知道我也将其放置，而我没有放置它的原因是因为它很长，所以我如何获得数组列表孩子们表演？谢谢你的时间。