AndroidManifest.xml

<!-- Adding WRITE_EXTERNAL_STORAGE permissions in the AndroidManifest.xml file-->
    <uses-permission
        android:name="android.permission.WRITE_EXTERNAL_STORAGE"
        tools:ignore="ScopedStorage" />

MainActivity.java

package com.learnoset.testproject;

import android.Manifest;
import android.annotation.SuppressLint;
import android.content.ContentValues;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.ContextCompat;
import androidx.core.content.FileProvider;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class MainActivity extends AppCompatActivity {

    Bitmap bitmapFile;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // getting Bitmap from res folder. Replace with your own Bitmap aimage
        bitmapFile = BitmapFactory.decodeResource(getResources(), R.drawable.image_file);

        // saving Bitmap Image to gallery
        saveImageToStorage();
    }


    @SuppressLint("NewApi")
    private void saveImageToStorage() {

        if (checkPermissions()) {

            final String fileName = "your_image_filename.jpg";

            OutputStream imageOutStream;

            try {

                // check if the Api level is greater than 29
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {

                    ContentValues values = new ContentValues();
                    values.put(MediaStore.Images.Media.DISPLAY_NAME, fileName);
                    values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg");

                    // save image to Pictures Directory
                    // You can also choose another directories like Environment.DIRECTORY_DCIM, Environment.DIRECTORY_DOWNLOADS, Environment.DIRECTORY_DOCUMENTS
                    values.put(MediaStore.Images.Media.RELATIVE_PATH, Environment.DIRECTORY_PICTURES);

                    Uri uri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
                    imageOutStream = getContentResolver().openOutputStream(uri);
                } else {
                    String imagesDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString();
                    File image = new File(imagesDir, fileName);
                    imageOutStream = new FileOutputStream(image);
                }

                // showing image to Gallery
                showingImageInGallery(fileName);

                // compress bitmap to Bitmap.CompressFormat.JPEG format you can also use Bitmap.CompressFormat.PNG format
                bitmapFile.compress(Bitmap.CompressFormat.JPEG, 100, imageOutStream);
                imageOutStream.close();
            } catch (IOException e) {
                Toast.makeText(this, "Image could not saved", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @SuppressLint("NewApi")
    private boolean checkPermissions() {

        boolean hasPermissions = false;

        // checking if user has granted Memory permissions or not. If not then ask for permissions.
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            hasPermissions = true;
        } else {

            // request for Memory permissions
            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE}, 101);
        }

        return hasPermissions;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        // Checking if user has granted memory permissions
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

            // save bitmap to memory if granted
            saveImageToStorage();
        }
    }

    private void showingImageInGallery(String imageFileName) {

        // getting image file path from external storage
        String imagesDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString();
        File image = new File(imagesDir, imageFileName);

        // converting file path to Uri
        Uri imageUri = FileProvider.getUriForFile(
                MainActivity.this,
                "com.your.application.id.fileprovider",
                image);

        // Scan Media Image File
        Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
        mediaScanIntent.setData(imageUri);
        sendBroadcast(mediaScanIntent);
    }
}