In Java what does before a method signature mean? [duplicate]

Answer 1

The means that there is a generic T being used in this declaration. This has two impacts;

• The T in the first type of the first argument must match the type in the second argument. (And ? super T means it must be a super class or interface of T) Without the use of a generic, there is no way to do this.
• The type can be given explicitly with a statement like Collections.sort(list, myComparator);