ExitManagerModule.java

packager your.package.name;

import android.app.Application;
import android.os.Process;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;

public class ExitManagerModule extends ReactContextBaseJavaModule {

    ReactApplicationContext reactContext;

    public ExitManagerModule(ReactApplicationContext reactContext) {
        super(reactContext);
        this.reactContext = reactContext;
    }

    @Override
    public String getName() {
        return "ExitManager";
    }

    @ReactMethod
    public void exitApp() {
        Process.killProcess(Process.myPid());
    }
}

ExitManagerPackage.java

package your.package.name;

import com.facebook.react.ReactPackage;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.uimanager.ViewManager;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ExitManagerPackage implements ReactPackage {

    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        return Collections.emptyList();
    }

    @Override
    public List<NativeModule> createNativeModules(
            ReactApplicationContext reactContext) {
        List<NativeModule> modules = new ArrayList<>();
        modules.add(new ExitManagerModule(reactContext));
        return modules;
    }

}

MainApplication.java

import <your.package.name>.ExitManagerPackage;

 @Override
protected List<ReactPackage> getPackages() {
  return Arrays.<ReactPackage>asList(
      new MainReactPackage(),
      new RNGestureHandlerPackage(),
      new ExitManagerPackage() // Add the package
  );
}