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Introduced in the Java JDK 1.2 release, the java.util.Iterator interface allows the iteration of container classes. Each Iterator provides a next() and hasNext() method, [18]: 294–295 and may optionally support a remove() [18]: 262, 266 method. Iterators are created by the corresponding container class, typically by a method named iterator().
The loop calls the Iterator::next method on the iterator before executing the loop body. If Iterator::next returns Some(_), the value inside is assigned to the pattern and the loop body is executed; if it returns None, the loop is terminated.
java.util.Collection class and interface hierarchy Java's java.util.Map class and interface hierarchy. The Java collections framework is a set of classes and interfaces that implement commonly reusable collection data structures. [1] Although referred to as a framework, it works in a manner of a library. The collections framework provides both ...
Java has had a standard interface for implementing iterators since its early days, and since Java 5, the "foreach" construction makes it easy to loop over objects that provide the java.lang.Iterable interface. (The Java collections framework and other collections frameworks, typically provide iterators for all collections.)
Here is a small excerpt from the definition of the interfaces java.util.List and java.util.Iterator in package java.util: interface List < E > { void add ( E x ); Iterator < E > iterator (); } interface Iterator < E > { E next (); boolean hasNext (); }
iterator.filter(pred) iterator is an Iterator and the filter method returns a new iterator; pred is a function (specifically FnMut) that receives the iterator's item and returns a bool: S, R: Filter(pred,array) array[pred(array)] In the second case, pred must be a vectorized function Scala: list.filter(pred)
Iterators constitute alternative language constructs to loops, which ensure consistent iterations over specific data structures. They can eventually save time and effort in later coding attempts. In particular, an iterator allows one to repeat the same kind of operation at each node of such a data structure, often in some pre-defined order.
thus the clause to 100 do ~ od, will iterate exactly 100 times. The while syntactic element allowed a programmer to break from a for loop early, as in: INT sum sq := 0; FOR i WHILE print(("So far:", i, new line)); # Interposed for tracing purposes. # sum sq ≠ 70↑2 # This is the test for the WHILE # DO sum sq +:= i↑2 OD