why null is assign to main and container in java code?

[Luz]

Hello friends,
I am second year Computer Science student. I recently started learning java language. I find java language very interesting. In one of the java book I have seen following code, but I didn't understand it.

JComponent container = menu == null ? popupMenus : menus;

I don't know why null is assign to main and container in java code? Please help me.
Thank you.

[Praetor]

In this code ternary operator is used. It is used to check for condition, if condition is right then you will get value before "?" and if condition is false then you will get value after "?". You can also write above code in the following ways.

JComponent containers;
if (menus == null) {
  containers = popupMenus;
} else {
  containers = menus;
}

[Katty]

Hey you have wrong code. You have to include following condition in parenthesis like "if (menu == null)" to fix this problem. In your code you have use ternary operator which is shorthand for an if-then-else statement, because it used three operands. If condition in If statement is right then first value is assigned to variable or if condition become false the second value assign to variable.

[kelfro]

It is one of the most complex version of ternary operator. It is very easy to understand. You can also right above code in the following ways.

JComponent container;
  if (menus == null)
       containers= popupMenu;
  else
       containers = menus;

Meaning of above code and your code is the same.

[Zecho]

JComponent containers = ((menus == null) ? popupMenus : menus);

This code compares menu with null. If condition is right then popupMenu is assigned to containers and if condition is wrong then menu is assign to containers.

[Modifier]

JComponent container = menu == null ? popupMenus : menus;

Meaning of above code is such that If menu is null then set container to popupMenu and if menu is something then set container to menu.