foreach loop a java creation?

Why was this loop introduced in java?Is 开发者_Go百科it a java creation? What is its purpose(increases memory/cpu utilisation efficiency)?

---

Why was this loop introduced in java?

It's just to ease looping over generic collections and arrays. Instead of

for (int i = 0; i < strings.length; i++) {
    String string = strings[i];
    // ...
}

you can just do

for (String string : strings) {
    // ...
}

which makes the code more readable and better maintainable.

Is it a java creation?

No, it existed in other languages long before Java. Java was relatively late in implementing it.

What is its purpose?

See the first answer.

To learn more about it, checkout the Sun guide on the subject.

Update: this does not mean that it makes the other kinds of loops superfluous. the for loop using index is still useful if you'd like to maintain a loop counter for other purposes than getting the item by index. The for loop using an iterator is still useful if you'd like to remove or change elements of the collection itself inside a loop.

---

It masks the use of iterators, which are heavy and clumsy to use. There are many, many instances where you just want to iterate over a collection without working about its index. The java foreach structure makes this possible.

---

Please see Foreach:

For each (or foreach) is a computer language idiom for traversing items in a collection. Foreach is usually used in place of a standard for statement. Unlike other for loop constructs, however, foreach loops 1 usually maintain no explicit counter: they essentially say "do this to everything in this set", rather than "do this x times". This avoids potential off-by-one errors and makes code simpler to read. In object-oriented languages an iterator, even if implicit, is often used as the means of traversal.

Several languages, including Python, have only a foreach loop, requiring explicit counting to achieve "standard" for behavior.

And specifically the section on Java:

A foreach-construct was introduced in JDK 5.0. Official sources use several names for the construct. It is referred to as the "Enhanced for Loop" the "For-Each Loop" and the "foreach statement".

---

It's really just Java's imitation of a functional construct that's been around much longer, it's called map. The reason for implementing it is that it is common to make a loop that simply performs an action to every element of a container without regard to it's index. Java's for(element : container) { doSomethingWith(element); } syntax is just a cleaner way to do it than the alternatives, which are either to make a for loop with an index

for(int i=0; i<container.size(); ++i) { doSomethingWith(container.at(i));  }

which is longer and creates a needless index variable, or to do a loop with an iterator

Iterator it = container.iterator(); 
while(it.hasNext()) { doSomethingWith(it.next()); }

which is also longer. This loop is essentially what the for( : ) {} loop gets compiled as, although there may be some slight differences (I haven't actually seen the bytecode).

---

It is plain "Syntactic sugar"

Dont think there is any efficiency improvement.

Java community wanted the language to be a bit modernized, competing with C# and Ruby..