how to see if element exists selenium code example

Example: isdisplayed in selenium

isDispalyed() -> verifies the presence of a web element within the web page. 
      		      If found -> true,   If not found ->  false	
		      checks for the presence of all kinds of web elements available
isEnabled()  -> verify if the web element is enabled or disabled within the 
                web page.
		       is primarily used with buttons
isSelected()   -> verifies if the web element is selected or not
		       is used with radio buttons, dropdowns and checkboxes.