It’s a bit of an oversimplification to say that the enhanced for loop is more efficient. It can be, but in many cases it’s almost exactly the same as an old-school loop. The first thing to note is that for collections the enhanced for loop uses an Iterator, so if you manually iterate over a … Read more
You need to implement the Iterable interface, which means you need to implement the iterator() method. In your case, this might look something like this: public class BookList implements Iterable<Book> { private final List<Book> bList = new ArrayList<Book>(); @Override public Iterator<Book> iterator() { return bList.iterator(); } … }
The for…in statement is meant to be used to iterate over object properties, by looking your code seems that actors is an Array (you are setting the initial element with index 0). This statement will also crawl up the prototype chain, if you have extended the Array.prototype those properties will be iterated, and also the … Read more
Use a label on the outermost loop, and include this label in the break statement when you want to jump out of all the loops. In the example below, I’ve modified your code to use the label OUTERMOST: String valueFromObj2 = null; String valueFromObj4 = null; OUTERMOST: for(Object1 object1: objects){ for(Object2 object2: object1){ //I get … Read more
Change your thought process from “append a line break all but the last time” to “prepend a line break all but the first time”: boolean first = true; StringBuilder builder = new StringBuilder(); for (Map.Entry<MyClass.Key,String> entry : data.entrySet()) { if (first) { first = false; } else { builder.append(“\n”); // Or whatever break you want … Read more
This problem is pretty debuggable, an uncommon luxury when you have problems with threads. Your basic tool here is the Debug > Windows > Threads debugger window. Shows you the active threads and gives you a peek at their stack trace. You’ll easily see that, once it gets slow, that you’ll have dozens of threads … Read more
because it is equivalent to using an iterator, it is equivalent to calling the collections’ . iterator() method, and it is called once.
You’re changing the iteration variable c. That doesn’t change the contents of the array. The iteration variable is just a copy of the array element. If you want to modify the array, you need to do so explicitly: for (int i = 0; i < array.length; i++) { if (array[i] == ‘o’) { array[i] = … Read more
for (Iterator<String> i = someIterable.iterator(); i.hasNext();) { String item = i.next(); System.out.println(item); } Note that if you need to use i.remove(); in your loop, or access the actual iterator in some way, you cannot use the for ( : ) idiom, since the actual iterator is merely inferred. As was noted by Denis Bueno, this … Read more