The ActionBar, also known as the Toolbar, is a crucial component of Android apps that provides a consistent and customizable way to present key actions and information to users. It serves as a primary navigation and control element in the app's user interface.
Adding a Toolbar to your Android app in Android Studio using Java involves a few simple steps. By following these steps, you can integrate a Toolbar and enhance your app's user experience by providing a feature-rich ActionBar.

Set up your project
Create a new project or open an existing one in Android Studio.

Add the Toolbar to your layout
In your activity layout XML file, add a Toolbar element where you want to display the ActionBar. For example:

<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="@color/colorPrimary"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar" />

Configure the Toolbar in your activity
In your activity or fragment class, find the Toolbar by its ID and set it as the ActionBar using the setSupportActionBar() method. For example:

Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

Customize the ActionBar
To customize the ActionBar appearance and behavior, you can modify the Toolbar attributes and apply styles or themes to it. You can also set the title, add a navigation button, and handle ActionBar actions.

// Set the title
getSupportActionBar().setTitle("My Toolbar");

// Enable the Up button (back navigation)
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

// Handle the Up button click event
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home) {
        // Handle Up button click here
        return true;
    }
    return super.onOptionsItemSelected(item);
}

Add menu items (optional)
You can add menu items to the ActionBar by creating a menu XML file and inflating it in the onCreateOptionsMenu() method. For example:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

// Handle menu item clicks
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        // Handle settings menu item click here
        return true;
    }
    return super.onOptionsItemSelected(item);
}

Customize ActionBar behavior (optional)
You can further customize the ActionBar behavior by overriding methods such as onPrepareOptionsMenu() or onOptionsItemSelected() to dynamically show or hide menu items or perform specific actions based on user interactions.

Another Written Description

In the res directory of your project, right-click on the menu folder and select "New" > "Android Resource File". Set the File name as menu_main and select "Menu" as the Resource type. Click "OK" to create the file.

Define menu items
Open the menu_main.xml file and define the menu items using the tag. Assign each item a unique ID and set the title and other properties as needed. For example:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_search"
        android:icon="@drawable/ic_search"
        android:title="Search"
        app:showAsAction="ifRoom" />

    <item
        android:id="@+id/action_settings"
        android:title="Settings"
        app:showAsAction="never" />

</menu>

Customize menu items
You can further customize the menu items by adding additional attributes or modifying existing ones. For example, you can set icons for the items using the android:icon attribute, set the visibility of items using the app:showAsAction attribute, and define click actions for each item.

Inflate the menu in your activity
In your activity or fragment class, override the onCreateOptionsMenu() method to inflate the menu_main.xml file and display the menu items in the ActionBar. For example:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

Handle menu item clicks
Override the onOptionsItemSelected() method to handle the click events for the menu items. Use the item ID to identify which item was clicked and perform the corresponding actions. For example:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_search) {
        // Handle search menu item click here
        return true;
    } else if (id == R.id.action_settings) {
        // Handle settings menu item click here
        return true;
    }
    return super.onOptionsItemSelected(item);
}

By following these steps, you can seamlessly integrate a Toolbar (ActionBar) into your Android Studio project using Java. The Toolbar provides a consistent and customizable ActionBar that enhances the usability and visual appeal of your app. Customize the ActionBar appearance, handle actions, and add menu items based on your app's requirements to create a cohesive and intuitive user experience.

In order to use the Toolbar as an ActionBar in your Android app, you need to include the appropriate dependencies in the build.gradle file of your app module. Here are the dependencies that you may need to add:

implementation 'androidx.appcompat:appcompat:1.6.1'
implementation 'com.google.android.material:material:1.8.0'

Make sure to sync your project after adding the dependency by clicking on the "Sync Now" button or selecting "Sync Project with Gradle Files" from the toolbar. By including the appcompat dependency, you ensure that your app can utilize the Toolbar as an ActionBar, giving you more control and flexibility over the app's navigation and user interface.