using java what is the usage of question mark ?

Question

what does the question mark do when added to the code .

Answer 1

You should ask a more descriptive question. But what comes to mind are ternary operations. In C# (and perhaps other languages) you can also use it to declare nullable types. eg. int? to declare a nullable integer. This can come in handy if returning null as a value from a database.

Answer 2

(Please make more descriptive question)

The best I can guess is "ternary function"
fruit = input=="apple"?apple:"not apple";