Android R Update:

From Android R, this method always returns false. Google says that this is done "to protect goat privacy":

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this method can
 * now automatically identify goats using advanced goat recognition technology.</p>
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#R}, this method always returns
 * {@code false} in order to protect goat privacy.</p>
 *
 * @return Returns whether the user making this call is a goat.
 */
public boolean isUserAGoat() {
    if (mContext.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.R) {
        return false;
    }
    return mContext.getPackageManager()
            .isPackageAvailable("com.coffeestainstudios.goatsimulator");
}

Previous answer:

From their source, the method used to return false until it was changed in API 21.

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 * @return whether the user making this call is a goat 
 */
public boolean isUserAGoat() {
    return false;
}

It looks like the method has no real use for us as developers. Someone has previously stated that it might be an Easter egg.

In API 21 the implementation was changed to check if there is an installed app with the package com.coffeestainstudios.goatsimulator

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this method can
 * now automatically identify goats using advanced goat recognition technology.</p>
 *
 * @return Returns true if the user making this call is a goat.
 */
public boolean isUserAGoat() {
    return mContext.getPackageManager()
            .isPackageAvailable("com.coffeestainstudios.goatsimulator");
}

Here is the source and the change.

Windows: Ctrl + Alt + L

Linux: Ctrl + Shift + Alt + L

macOS: Option + Command + L

Reference: Key Commands and here are all of the commands for Windows/ Linux users and for Mac users.

As Rohit faced a problem in Ubuntu with the format code shortcut, this is due to the Ctrl + Alt + L key being used to lock the screen in Ubuntu.

I found that Ubuntu handles this keyboard shortcut first. So you should bind the Ctrl + Alt + L keyboard shortcut to something else so that it doesn't conflict with Ubuntu.

Steps

1. Go to System Tools → System Settings → Keyboard → Shortcuts tab → System → Lock Screen.

2. Select the row New Accelerator..., then press any special key with the Alpha key (e.g. Shift + L). You should've successfully changed the keyboard shortcut.

3. Check if the keyboard shortcut now works in Android Studio.

Alternative method

Ctrl + Alt + Shift + L (to show a dialog)

You can also use Eclipse shortcuts.

• Windows and Linux: Go to menu File → Settings → Keymap
• macOS: Go to menu Preferences → Keymap and choose Eclipse from the drop-down menu.

Using MenuBar

• Select code which you want to reformat

• Click on Code in the menu bar and select Reformat Code as shown in the image below:

  

In Android studio 3.5, there is problem with rearranging the xml code, it also rearrange the views as well, so need to use these settings first.

Settings -> Editor -> Code Style -> XML-> Set From -> Predefined Style > Android.

Update for Android Studio 4+

Since Android Studio 4+, you might face issue shortcuts on mac. Shortcuts not working after updating to Android studio 4, in Mac? have an answer for that.