instantiation of FragmentTransaction object not possble according to the compiler, Android

when I try to instantiate FragmentTransaction() I the the error message:

"can not instantiate the type FragmentTransaction"

in google Android reference it states:

Public Constructors

FragmentTransaction()

so if there is a constructor of FragmentTransaction() then it must be possible to do this,

 FragmentTransaction fragtransaction = new FragmentTransaction();

the question is WHY is this not possible?

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