The latest, release of Eclipse has removed Navigator which is a very crucial feature for developers help to them navigate through files and folders.

However, it can customize Project Explorer as needed.

• Click on the three dots which is in the top right-hand corner just in front of your project in the Project Explorer tab.
• Under Pre-set filters uncheck Java output folders.
• Finally, under Content uncheck Java Element.

Now can work as expected as Navigator before.