RoomDatabase

//Gradle(module)
plugins {
    alias(libs.plugins.android.application)
}

android {
    namespace = "com.example.room"
    compileSdk = 35

    defaultConfig {
        applicationId = "com.example.room"
        minSdk = 24
        targetSdk = 35
        versionCode = 1
        versionName = "1.0"

        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            isMinifyEnabled = false
            proguardFiles(
                getDefaultProguardFile("proguard-android-optimize.txt"),
                "proguard-rules.pro"
            )
        }
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_11
        targetCompatibility = JavaVersion.VERSION_11
    }
}

dependencies {

    implementation(libs.appcompat)
    implementation(libs.material)
    implementation(libs.activity)
    implementation(libs.constraintlayout)
    implementation(libs.room.common)
    testImplementation(libs.junit)
    androidTestImplementation(libs.ext.junit)
    androidTestImplementation(libs.espresso.core)
    implementation(libs.androidx.room.runtime)//add this
    annotationProcessor(libs.androidx.room.compiler)


}




MainActivity.java
 package com.example.room;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

import java.util.ArrayList;

 public class MainActivity extends AppCompatActivity {
EditText editText,editText2;
Button btnNext;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            editText=findViewById(R.id.editText);
            editText2=findViewById(R.id.editText2);
            btnNext=findViewById(R.id.btnNext);
            Dtabasehelper databaseHelper = Dtabasehelper.getDB(this);
            btnNext.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String title =editText.getText().toString();
                    String amount=editText2.getText().toString();
                    databaseHelper.expensedao().addTx(
                            new Expense(title,amount) // id is autogennerated user give only title and amount thus constructor of 2 p is used
                    );
                   ArrayList<Expense>arrExpenses =(ArrayList<Expense>) databaseHelper.expensedao().getAllExpense();
                   for(int i=0;i<arrExpenses.size();i++){
                       Log.d("Data","Title:"+arrExpenses.get(i).getTitle()+"Amount: "+arrExpenses.get(i).getAmount()+"ID: "+arrExpenses.get(i).getId());
                   }
                }
            });


            return insets;
        });
    }
}




Databasehelper.java(abstract class)
package com.example.room;

import android.content.Context;

import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;
@Database(entities = Expense.class, exportSchema = false, version = 1)
abstract class Dtabasehelper extends RoomDatabase {
    private static final String DB_NAME = "expensedb";// file name
    private static Dtabasehelper instance;

    public static synchronized Dtabasehelper getDB(Context context) {
        if (instance == null) {
            instance = Room.databaseBuilder(context.getApplicationContext(), Dtabasehelper.class, DB_NAME)
                    .fallbackToDestructiveMigration()// create new database sometimes where it cannot perform migration
                    .allowMainThreadQueries()// Brings UI to main thread
                    .build();
        }
        return instance;
    }

    public abstract Expensedao expensedao();
}




Expense.java
package com.example.room;

import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.Ignore;
import androidx.room.PrimaryKey;

@Entity(tableName = "expense")// Entity for table
public class Expense {
    @PrimaryKey(autoGenerate = true)
    private int id;
    @ColumnInfo(name="title")
    private String title;
    @ColumnInfo(name="amount")
    private String amount;
    Expense(int id,String title,String amount) {
        this.id = id;
        this.amount = amount;
        this.title = title;
    }
    @Ignore// Skip this
        Expense(String title,String amount){
            this.title=title;
            this.amount=amount;
        }

    public int getId() {
        return id;
    }

    public String getAmount() {
        return amount;
    }

    public String getTitle() {
        return title;
    }

    public void setAmount(String amount) {
        this.amount = amount;
    }

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

    public void setTitle(String title) {
        this.title = title;
    }
}




Expensedao(Interface)
package com.example.room;

import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;

import java.util.List;

@Dao

public interface Expensedao {
    @Query("select * from expense")
    List<Expense> getAllExpense();



    @Insert
    void addTx(Expense expense);

    @Update
    void updateTx(Expense expense);

    @Delete
    void deleteTx(Expense expense);
}