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Some iterator basics and how concurrent modification errors happen
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| import java.util.*; | |
| import java.util.ArrayList; | |
| import java.util.Collection; | |
| import java.util.Iterator; | |
| class Main { | |
| public static void main(String[] args) { | |
| System.out.println("Hello world!"); | |
| Collection<Dog> doggos = new ArrayList<>(); | |
| doggos.add(new Dog("Fido")); | |
| doggos.add(new Dog("Spot")); | |
| doggos.add(new Dog("Lucy")); | |
| System.out.println(doggos); | |
| for (Dog d : doggos) { | |
| if (d.name.equals("Spot")) { | |
| System.out.println(d.toString()); | |
| } | |
| } | |
| Iterator<Dog> dogIterator = doggos.iterator(); | |
| while (dogIterator.hasNext()) { | |
| if (dogIterator.next().name.equals("Spot")) { | |
| //doggos.add(new Dog("Spotty Doggo")); /// ConcurrentModificationException | |
| //dogIterator.add(new Dog("Spotty Doggo")); /// Cannot find symbol compiler error | |
| //doggos.remove(dogIterator.next()); // ConcurrentModificationException | |
| dogIterator.remove(); // Spot went off to the big farmhouse in the sky. | |
| } | |
| } | |
| System.out.println(doggos); | |
| } | |
| } | |
| class Dog { | |
| String name; | |
| Dog(String dogName) { | |
| name = dogName; | |
| } | |
| @Override | |
| public String toString() { | |
| return ("Am dog named " + name); | |
| } | |
| } | |
| class C { | |
| public static void main(String[] args) { | |
| Set<String> set = new HashSet<String>(); | |
| for (String arguments : args) /// For every argument given | |
| if (!set.add(arguments)) /// If the set does not already have a copy of a given argument, add it to the list. It it's already in the list, continue to... | |
| System.out.println("Already in the set: " + arguments); /// ...print it on the next line | |
| System.out.println(set.size() + " in set: " + set); /// Then print out the set | |
| } | |
| } |
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