i can't solve my Error i'm doing CHECKBOX in recyclerview :     '''
    package com.example.project.Holder;
    
    import android.content.Context;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.CheckBox;
    import android.widget.ImageView;
    import android.widget.TextView;
    import android.widget.Toast;
    
    import androidx.annotation.NonNull;
    import androidx.recyclerview.widget.LinearLayoutManager;
    import androidx.recyclerview.widget.RecyclerView;
    
    import com.bumptech.glide.Glide;
    import com.bumptech.glide.request.RequestOptions;
    import com.example.project.Model.User;
    import com.example.project.R;
    
    import java.util.List;
    
    public class AttendanceViewHolder {
    
        private Context mContext;
        private UserAdapter userAdapter;
    
    
        public void setConfig(RecyclerView recyclerView,Context context,List<User> users,List<String> keys){
            mContext=context;
            userAdapter=new UserAdapter(users,keys);
            recyclerView.setLayoutManager(new LinearLayoutManager(context));
            recyclerView.setAdapter(userAdapter);
        }
        class UserItemView extends RecyclerView.ViewHolder {
            public ImageView attendanceitem_imageview;
            private TextView attendanceitem_textview;
            private String key;
            public CheckBox attendance_checkBox;
    
            public UserItemView(ViewGroup parent) {
                super(LayoutInflater.from(mContext).
                        inflate(R.layout.item_attendance_bottom, parent, false));
                attendanceitem_imageview = (ImageView) itemView.findViewById(R.id.attendanceitem_imageview);
                attendanceitem_textview = (TextView) itemView.findViewById(R.id.attendanceitem_textview);
                attendance_checkBox =(CheckBox) itemView.findViewById(R.id.attendance_checkBox);
            }
    
            public void bind(User user, String key) {
    
                attendanceitem_textview.setText(user.getUsername());
    
                this.key = key;
            }
    
        }
        class UserAdapter extends RecyclerView.Adapter<UserItemView> {
                 List<User> userList;
                private  List<String> mkeys;
    
                public UserAdapter(List<User> userList, List<String> mkeys) {
                    this.userList = userList;
                    this.mkeys = mkeys;
    
    
                }
    
                @NonNull
                @Override
                public UserItemView onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    
                    return new UserItemView(parent);
                }
    
                @Override
                public void onBindViewHolder(@NonNull UserItemView holder, int position) {
                    final int pos = position;
                    holder.attendance_checkBox.setChecked(userList.get(position).isCheckBox());
                    holder.attendance_checkBox.setTag(userList.get(position));
                    holder.bind(userList.get(position),mkeys.get(position));
                    Glide.with(holder.attendanceitem_imageview.getContext())
                            .load(userList.get(position).profileImageUrl)
                            .apply(new RequestOptions())
                            .into(holder.attendanceitem_imageview);
                    holder.attendance_checkBox.setOnClickListener(new View.OnClickListener() {
                        public void onClick(View view) {
                            CheckBox attendance_checkBox = (CheckBox) view;
                            User contact = (User) attendance_checkBox.getTag();
    
                            contact.setCheckBox(attendance_checkBox.isChecked());
                            userList.get(pos).setCheckBox(attendance_checkBox.isChecked());
                        }
                    });
                }
    
                @Override
                public int getItemCount() {
                    return userList.size();
                }
            }
    
    
    
    
    
    }
    '''
    package com.example.project.Model;
    
    import android.net.Uri;
    import android.widget.ImageView;
    
    public class User {
        public String email;
        public String profileImageUrl;
        public String username;
        public String uid;
        public String pushToken;
        public String job;
        public String comment;
        public Boolean checkBox;
    
        public User() {
        }
    
        public String getEmail() {
            return email;
        }
    
        public void setEmail(String email) {
            this.email = email;
        }
    
    
        public String getProfileImageUrl() {
            return profileImageUrl;
        }
    
        public void setProfileImageUrl(String profileImageUrl) {
            this.profileImageUrl = profileImageUrl;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getUid() {
            return uid;
        }
    
        public void setUid(String uid) {
            this.uid = uid;
        }
    
        public String getPushToken() {
            return pushToken;
        }
    
        public void setPushToken(String pushToken) {
            this.pushToken = pushToken;
        }
    
        public String getJob() {
            return job;
        }
    
        public void setJob(String job) {
            this.job = job;
        }
    
        public String getComment() {
            return comment;
        }
    
        public void setComment(String comment) {
            this.comment = comment;
        }
    
        public boolean isCheckBox() {
            return checkBox;
        }
    
        public void setCheckBox(Boolean chechBox) {
            this.checkBox = chechBox;
        }
    }
    '''
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
        at com.example.project.Model.User.isCheckBox(User.java:77)
        at com.example.project.Holder.AttendanceViewHolder$UserAdapter.onBindViewHolder(AttendanceViewHolder.java:80)
        at com.example.project.Holder.AttendanceViewHolder$UserAdapter.onBindViewHolder(AttendanceViewHolder.java:58)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6937)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6979)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5896)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6163)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6002)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5998)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2226)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1558)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1518)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:613)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4033)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3750)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4303)
        at android.view.View.layout(View.java:21927)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:21927)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:21927)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:21927)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:779)
        at android.view.View.layout(View.java:21927)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3080)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2590)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
        at android.view.Choreographer.doCallbacks(Choreographer.java:790)
        at android.view.Choreographer.doFrame(Choreographer.java:725)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
'''