Detecting the amount the status bar and navigation bars affect the screen area on Android

ScreenUtils.java

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Point;
import android.os.Build;
import android.support.annotation.NonNull;
import android.view.Display;
import android.view.WindowManager;

import java.lang.reflect.InvocationTargetException;

public class ScreenUtils {

	/**
	 * Whether or not a display is in landscape.
	 * <pre>
	 *     Display display = activity.getWindowManager().getDefaultDisplay();
	 *     boolean isLandscape = isLandscape(display);
	 * </pre>
	 *
	 * @return whether or not the screen is in landscape mode
	 */
	public boolean isLandscape(@NonNull Display display) {
		Point point = new Point();
		display.getSize(point);
		return point.x > point.y;
	}

	/**
	 * Get the height of the status bar
	 */
	public static int getStatusBarHeight(@NonNull Context context) {
		int result = 0;
		Resources resources = context.getResources();
		int resourceId = resources.getIdentifier("status_bar_height", "dimen", "android");
		if (resourceId > 0) {
			result = resources.getDimensionPixelSize(resourceId);
		}
		return result;
	}

	/**
	 * Get the width of a navigation bar on the right, or the height of a navigation bar on the bottom.
	 */
	public static Point getNavigationBarEffect(@NonNull Context context) {
		Point appUsableSize = getAppUsableScreenSize(context);
		Point realScreenSize = getRealScreenSize(context);

		// navigation bar on the right
		if (appUsableSize.x < realScreenSize.x) {
			return new Point(realScreenSize.x - appUsableSize.x, 0);
		}

		// navigation bar at the bottom
		if (appUsableSize.y < realScreenSize.y) {
			return new Point(0, realScreenSize.y - appUsableSize.y);
		}

		// navigation bar is not present
		return new Point();
	}

	private static Point getAppUsableScreenSize(@NonNull Context context) {
		WindowManager windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
		Display display = windowManager.getDefaultDisplay();
		Point size = new Point();
		display.getSize(size);
		return size;
	}

	private static Point getRealScreenSize(@NonNull Context context) {
		WindowManager windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
		Display display = windowManager.getDefaultDisplay();
		Point size = new Point();

		if (Build.VERSION.SDK_INT >= 17) {
			display.getRealSize(size);
		} else if (Build.VERSION.SDK_INT >= 14) {
			try {
				size.x = (Integer) Display.class.getMethod("getRawWidth").invoke(display);
				size.y = (Integer) Display.class.getMethod("getRawHeight").invoke(display);
			} catch (IllegalAccessException e) {
			} catch (InvocationTargetException e) {
			} catch (NoSuchMethodException e) {
			}
		}

		return size;
	}

}

If Navigation bar is not visible for Android P (Navigation Gesture) then navigation height will be zero but I can't get zero. Can you help in this?