Is there a way in Java's for-each loop
for(String s : stringArray) {
doSomethingWith(s);
}
to find out how often the loop has already been processed?
Aside from using using the old and well-known for(int i=0;i<boundary;i++)-loop, is the construct
int i = 0;
for(String s : stringArray) {
doSomethingWith(s);
i++;
}
the only way to have such a counter available in a for-each loop?
Why can't I do:
Enumeration e = ...
for (Object o : e)
...
I thought I'd offer this softball to whomever would like to hit it out of the park. What are generics, what are the advantages of generics, why, where, how should I use them? Please, keep it fairly basic. Thanks.
Well, I'm pretty much trying to figure out how to pull information from a webpage, and bring it into my program (in Java).
For example, if I know the exact page I want info from, for the sake of simplicity a Best Buy item page, how would I get the appropriate info I need off of that page? Like the title, price, description?
What would this process even be called? I have no idea were to even...
I often have a need to take a list of objects and group them into a Map based on a value contained in the object. Eg. take a list of Users and group by Country.
My code for this usually looks like:
Map<String, List<User>> usersByCountry = new HashMap<String, List<User>>();
for(User user : listOfUsers) {
if(usersByCountry.containsKey(user.getCountry())) {
//...
Does a java for-each loop guarantee that the elements will be presented in order if invoked on a list? In my tests it does seem to, but I can't seem to find this explicitly mentioned in any documentation
List<Integer> myList;// [1,2,3,4]
for (Integer i : myList) {
System.out.println(i.intValue());
}
#output
1,2,3,4
I created a class MyList that has a field
private LinkedList<User> list;
I would like to be able to iterate the list like this:
for(User user : myList) {
//do something with user
}
(when my list is an instance of MyList).
How? What should I add to my class?
I think most coders have used code like the following :
ArrayList<String> myStringList = getStringList();
for(String str : myStringList)
{
doSomethingWith(str);
}
How can I take advantage of the for each loop with my own classes? Is there an interface I should be implementing?
How do I get the current index for the song element in Java?
for (Element song: question){
song.currentIndex() ??
}
In PHP you could do
foreach ($arr as $index => $value) {
echo "Key: $index; Value: $value";
}
if I do this in Java:
for(String s : myCollection.expensiveListGeneration())
{
doSomething();
}
is expensiveListGeneration() invoked just once at the beggining or in every cycle iteration?
Is it implementation dependent?
This might be a bit silly, but where can I find a reference (not code) that tells me, what classes (in the .NET-Framework) implement an interface? Is this even available?
I am thinking of the list one gets in the Java-API-documentation unter "All Known Implementing Classes" (like here for example: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Iterable.html).
Currently I am wondering what ...
I have this for-each-loop:
for (Component c : container.getComponents()) {
// Loop code
}
Is getComponents called on every iteration? Does it make sense to call getComponents before the look and only work on a cached array?
def array = [1,2,3,4,5]
println 3 in array
prints true. What do I need to overload to support in for any object?
Example:
class Whatever {
def addItem(item) {
// add the item
}
}
def w = new Whatever()
w.addItem("one")
w.addItem("two")
println "two" in w
I know I could make the collection this class uses public, but I'd like to use in instead.
I am a beginner and I cannot understand the real effect of the Iterable interface.
I can't keep wondering why I can't write something like that:
for (int i : 3) {
System.out.println(i);
}
to print out:
0
1
2
I mean, 3 could be auto-boxed into an Integer, which could be Iterable.
I know, I've selected the first element to be 0, but I assume it's the common case and that it could facilitate counting down with such ForEach construct.
Sorry for the newbie question, I'm used to C# so my Java framework knowledge is not so good.
I have a couple of arrays:
int[] numbers = new int[10];
String[] names = new String[10];
//populate the arrays
Now I want to make a generic function which will print out the values in these arrays, something like the following (this should work in C#)
private void PrintAll(IEnumerable items)
{ ...
OK, so it's easy to name an interface (or class for that matter) if you can easily think of a noun: User, Window, Database, Stream, etc.
What about an adjective or adjective concept? e.g. something that has a timestamp (HasTimestamp, Timestamped, Timestampable...?) or something that is tracked or watched (Trackable, IsTracked, Watchable, IsWatched...?)
The Java Collections.max takes only a collection of a sortable object. However since the collection is not necessarily sorted, I don't see any reason not to implement the same max function for iterable types.
Is there a max method for Iterable<T extends Comparable<? super T>> in java's standard library?
If javac do what I think, the following lines would yield the same performance:
for (Object o: getObjects()) {}
List<Object> os = getObjects(); for (Object o: os) {}
Is it so or not? Or is it perhaps implementation-specific? If so: anybody know about GWT?
Suppose I have a base class B, and a derived class D. I wish to have a method foo() within my base class that returns a new object of whatever type the instance is. So, for example, if I call B.foo() it returns an object of type B, while if I call D.foo() it returns an object of type D; meanwhile, the implementation resides solely in the base class B.
Is this possible?
I get this error when trying to compile:
The method filter(Iterable<T>, Predicate<? super T>) in the type Iterables is not applicable for the arguments (Iterator<PeopleSoftBalance>, ColumnLikePredicate<PeopleSoftBalance>)
Here is the ColumnLikePredicate class sig:
public class ColumnLikePredicate<T extends RowModel> implements Predicate<T>
What am I ...
