is iterator an interface in java?
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'Iterator' is an interface which belongs to collection framework. It allows us to traverse the collection, access the data element and remove the data elements of the collection.
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Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions ( yield statements, in Python 2.5 and earlier), and is an object that meets the previous paragraph's definition of an iterator .
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The Java for-each loop or enhanced for loop is introduced since J2SE 5.0. It provides an alternative approach to traverse the array or collection in Java. It is mainly used to traverse the array or collection elements.
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Comparator interface belongs to java. util package while comparable belongs to java. lang package. Comparator interface sort collection using two objects provided to it, whereas comparable interface compares" this" refers to the one objects provided to it.
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Java 8Object Oriented ProgrammingProgramming. The mapToInt() method returns an IntStream consisting of the results of applying the given function to the elements of this stream. The syntax is as follows mapToInt(LongToIntFunction mapper) Here, the parameter mapper is the stateless function applied to each element.
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Explanation: All primitive wrapper classes (Integer, Byte, Long, Float, Double, Character, Boolean and Short) are immutable in Java, so operations like addition and subtraction create a new object and not modify the old.
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ArrayList simply stores object references. As a generic collection, List<T> implements the generic IEnumerable<T> interface and can be used easily in LINQ (without requiring any Cast or OfType call). ArrayList belongs to the days that C# didn't have generics. It's deprecated in favor of List<T> .
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IEnumerable doesn't allow random access, where as List does allow random access using integral index. In term of performance, iterating values from IEnumerable is much faster than iterating values from a List.
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In fact, all collection classes (except Vector and Hashtable) in the java. util package are not thread-safe. ... That's why the new collections (List, Set, Map, etc) provide no concurrency control at all to provide maximum performance in single-threaded applications.
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The order in which the elements contained in a Java Iterator are traversed depends on the object that supplies the Iterator . For instance, an iterator obtained from a List will iterate through the elements of that List in the same order the elements are stored internally in the List .
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The reason to use IList instead of List as parameters, is because many things implement IList (List and [], as two examples), but only one thing implements List . It's more flexible to code to the interface. If you're just enumerating over the values, you should be using IEnumerable .
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In for-each loop, we can't modify collection, it will throw a ConcurrentModificationException on the other hand with iterator we can modify collection. Modifying a collection simply means removing an element or changing content of an item stored in the collection.
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IList on the other hand is an Interface. Basically, if you want to create your own type of List, say a list class called BookList, then you can use the Interface to give you basic methods and structure to your new class. IList is for when you want to create your own, special sub-class that implements List.
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No. POJO class can implement any interface, or implement no interface. It can extend any class (note any user-defined class extends some other class, probably java. lang.
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The difference to List now is that List is untyped and therefore no type checks at all are performed, which ultimately leads to certain warnings and can lead to weird runtime behavior. While Java knows that List<Object> is a list that might contain anything, it doesn't know that about a List .
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In the example of the micro-benchmark given, the reason the Enumeration is faster than Iterator is because it is tested first. ;) The longer answer is that the HotSpot compiler optimises a whole method when a loop has iterated 10,000 times.
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Python map() function is used to apply a function on all the elements of specified iterable and return map object. Python map object is an iterator, so we can iterate over its elements. We can also convert map object to sequence objects such as list, tuple etc. using their factory functions.