Traverse the Set (ilist) in Java, C #, and C ++)

In Java, the common way to traverse a set is as follows:

Iterator iter = List. iterator ();
While (ITER. hasnext ()){
Object item = ITER. Next ();
}

You can also use

For (iterator iter = List. iterator (); ITER. hasnext ()){
Object item = ITER. Next ();
}

Enhanced for syntax introduced by JDK 1.5

List list =
For (integer item: List ){
}

In C #, the way to traverse the set is as follows:

Foreach (Object item in List)
{
}

You can write like this, but there are very few people writing like this.

Ienumerator E = List. getenumerator ();
While (E. movenext ())
{
Object item = E. Current;
}

In C #2.0, foreach can perform a certain degree of compile-time type check. For example:

Ilist <int> intlist =
Foreach (string item in intlist) {}// compilation Error

In the C ++ standard library. For_each is an algorithm. Definition:
For_each (inputiterator beg, inputiterator end, unaryproc OP)
In C ++, the operator () can be overloaded, so there is a special object that is similar to a function.

Template <class T>
Class addvalue {
PRIVATE:
T thevalue;
Public:
Addvalue (const T & V): thevalue (v ){
}

Void operator () (T & ELEM) const {
ELEM + = thevalue;
}
};

Vector <int> V;
Insert_elements (V, 1, 9 );

For_each (V. Begin (), V. End (), addvalue <int> (10 ));