uname = (EditText) findViewById(R.id.UserName);
            pass  = (EditText) findViewById(R.id.Pass);
            phon  = (EditText) findViewById(R.id.PhoneNo);
            post= (EditText) findViewById(R.id.Pos);

            String un,pas,ph,pos;
            un = uname.getText().toString();
            pas = pass.getText().toString().trim();
            ph = phon.getText().toString().trim();
            pos = post.getText().toString().trim();

            final FirebaseUserForInformation fb = new FirebaseUserForInformation();

            fb.setuN(un.trim());
            fb.setPs(pas);
            fb.setPhNo(ph);
            fb.setPost(pos);

FirebaseDatabase database = FirebaseDatabase.getInstance();
                        DatabaseReference myRef = database.getReference("users");
myRef.push().setValue(fb);

and my FirebaseUserForInformation class is:

public class FirebaseUserForInformation{

    public FirebaseUserForInformation(){
        //constructor
    }


    public void setuN(String username){this.Username = username;}
    public void setPs(String password){ this.PassWord = password;}
    public void setPhNo(String ph){
        this.phoneNumber = ph;
    }
    public void setPost(String pos){
        this.post = pos;
    }

    public String getUN(){return Username;}
    public String getPs(){return PassWord;}
    public String getPhNo(){return phoneNumber;}
    public String getposNo(){return post;}


    private String Username;
    private String PassWord;
    private String phoneNumber;
    private String post;

}