How the variables name converted as text for child node creation in case of Firebase database?

Question

I am using the following Android code and that is working fine, there is no issue but I have a question.

How the variables name (such as: name,course,duration) converted as text for node creation as give in the following image:

The XML code:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="center_horizontal"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--        android:id="@+id/btn"-->

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="process"
        android:text="save to database"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.491"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.66"
        tools:ignore="MissingConstraints,OnClick" />

    <EditText
        android:id="@+id/t2"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:hint="enter your name"
        android:textColor="#000"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.495"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.172"
        tools:ignore="MissingConstraints" />

    <EditText
        android:id="@+id/t3"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:hint="enter your course"
        android:textColor="#000"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.522"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.298"
        tools:ignore="MissingConstraints" />

    <EditText
        android:id="@+id/t4"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:hint="enter your duration"
        android:textColor="#000"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.504"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.429"
        tools:ignore="MissingConstraints" />

    <EditText
        android:id="@+id/t1"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:hint="enter your roll number"
        android:textColor="#000"
        android:textSize="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.495"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.041"
        tools:ignore="MissingConstraints" />


</androidx.constraintlayout.widget.ConstraintLayout>

Code of MainActivity.java:

package com.example.application_for_curd;    
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {
    EditText t1,t2,t3,t4;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void process(View v){
        t1 = findViewById(R.id.t1);
        t2 = findViewById(R.id.t2);
        t3 = findViewById(R.id.t3);
        t4 = findViewById(R.id.t4);
        String roll = t1.getText().toString().trim();
        String name = t2.getText().toString().trim();
        String course = t3.getText().toString().trim();
        String duration = t4.getText().toString().trim();

        dataholder obj = new dataholder(name,course,duration);
        FirebaseDatabase db = FirebaseDatabase.getInstance();
        DatabaseReference node = db.getReference("students");

        node.child(roll).setValue(obj);

        t1.setText("");
        t2.setText("");
        t3.setText("");
        t4.setText("");

        Toast.makeText(getApplicationContext(),"values inserted", Toast.LENGTH_LONG).show();
    }
}

code for dataholder.java:

package com.example.application_for_curd;    
public class dataholder {
    String name,course,duration;

    public dataholder(String name, String course, String duration) {
        this.name = name;
        this.course = course;
        this.duration = duration;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCourse() {
        return course;
    }

    public void setCourse(String course) {
        this.course = course;
    }

    public String getDuration() {
        return duration;
    }

    public void setDuration(String duration) {
        this.duration = duration;
    }
}

How the variables name going to be converted as the text for the creation of child nodes, that can be seen by an attached image which consists of child node named as name, course, duration.

Answer 1

According to your last comment:

but name, course, duration these are the variables of string that are not a string

I understand that you want to have in your database values for your fields according to their corresponding data types. The "name" and "course" make sense to be of type String, however, the "duration" should be added as a number. You can save two different types of values into a property of type number, "long" values and "double" values. To achieve this, you should change the type of the property in your "dataholder" class to be of type "long" for example, and not String. The same rules apply in the case of a double value. So you should have the following declaration:

private String name, course;
private long duration;

And here is the corresponding getter and setter:

public long getDuration() {
    return duration;
}

public void setDuration(long duration) {
    this.duration = duration;
}

And your constructor should look like this:

public dataholder(String name, String course, long duration) {
    this.name = name;
    this.course = course;
    this.duration = duration;
}

Now to save the value for "duration" as a number and not as a String, please change the following line of code:

String duration = t4.getText().toString().trim();

To:

long duration = Long.parseLong(t4.getText().toString().trim());

With these changes, a value like "2 years" is not allowed anymore, as it's a String and not a number. So be aware to change all "duration" properties in the database to hold numbers and not String values.