The property (fields and getter/setter) names in your Java class don’t match up with the ones in your database. You can explicitly map the class to the database with Java annotations:

public class CategoryModel {
    private String categoryIconLink;
    private String categoryName;

    public CategoryModel() { }

    public CategoryModel(String categoryIconLink, String categoryName) {
        this.categoryIconLink = categoryIconLink;
        this.categoryName = categoryName;
    }

    @PropertyName("img")
    public String getCategoryIconLink() {
        return categoryIconLink;
    }

    @PropertyName("name")
    public String getCategoryName() {
        return categoryName;
    }

    @PropertyName("img")
    public void setCategoryIconLink(String categoryIconLink) {
        this.categoryIconLink = categoryIconLink;
    }

    @PropertyName("name")
    public void setCategoryName(String categoryName) {
        this.categoryName = categoryName;
    }
}

And you also need a no-argument constructor, as otherwise Firebase doesn’t know how to instantiate your class. So that’s the public CategoryModel() { } I added.

I stuck on one point please help me to solve this I need to send cateModelList to my adaptor in required format which consists of parameters 1) String type link 2) String type category name

I got data from firebase, I did not understand how can I format this data into my required list in for loop please help me

List<CategoryModel> categoryModelList = new ArrayList<CategoryModel>();

FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference databaseReference = database.getReference("categories");

        // Read from the database
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                for(DataSnapshot data:dataSnapshot.getChildren()){

                    categoryModelList.add(new CategoryModel(data.child().getValue("img"), data.child().getValue("name")))
                }

            }

            @Override
            public void onCancelled(DatabaseError error) {}
        });

Modal class

package com.e.mymallapp.ui.home;

public class CategoryModel {

    private String categoryIconLink;
    private String categoryName;

    public CategoryModel(String categoryIconLink, String categoryName) {
        this.categoryIconLink = categoryIconLink;
        this.categoryName = categoryName;
    }

    public String getCategoryIconLink() {
        return categoryIconLink;
    }

    public String getCategoryName() {
        return categoryName;
    }

    public void setCategoryIconLink(String categoryIconLink) {
        this.categoryIconLink = categoryIconLink;
    }

    public void setCategoryName(String categoryName) {
        this.categoryName = categoryName;
    }


}

firebase DB structure

Needed Output

List<CategoryModel> categoryModelList = new ArrayList<CategoryModel>();
        categoryModelList.add(new CategoryModel("link","Home"));
        categoryModelList.add(new CategoryModel("link","Electronics"));
        categoryModelList.add(new CategoryModel("link","Essentials"));
        categoryModelList.add(new CategoryModel("link","Grocery"));
        categoryModelList.add(new CategoryModel("link","Mobile"));
        categoryModelList.add(new CategoryModel("link","Fashion"));
        categoryModelList.add(new CategoryModel("link","Beauty"));
        categoryModelList.add(new CategoryModel("link","Appliances"));
        categoryModelList.add(new CategoryModel("link","Toys & Baby"));
        categoryModelList.add(new CategoryModel("link","Flight"));
        categoryModelList.add(new CategoryModel("link","Sports"));

Guys please help me I did not understand how can I get this type of list from this data