publicstaticvoidmain(String[] args) { List<String> list = new ArrayList<>(); for (int i = 0 ; i < 10 ; i++ ) { list.add(i + ""); } Iterator<String> iterator = list.iterator(); int i = 0 ; while(iterator.hasNext()) { if (i == 3) { list.remove(3); } System.out.println(iterator.next()); i ++; } }
/** * An optimized version of AbstractList.Itr */ privateclassItr implements Iterator<E> { int cursor; // index of next element to return int lastRet = -1; // index of last element returned; -1 if no such int expectedModCount = modCount;
publicbooleanhasNext(){ return cursor != size; } @SuppressWarnings("unchecked") public E next(){ checkForComodification(); int i = cursor; if (i >= size) thrownewNoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) thrownewConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; } publicvoidremove(){ if (lastRet < 0) thrownewIllegalStateException(); checkForComodification(); try { ArrayList.this.remove(lastRet); cursor = lastRet; lastRet = -1; expectedModCount = modCount; } catch (IndexOutOfBoundsException ex) { thrownewConcurrentModificationException(); } } @Override @SuppressWarnings("unchecked") publicvoidforEachRemaining(Consumer<? super E> consumer){ Objects.requireNonNull(consumer); finalint size = ArrayList.this.size; int i = cursor; if (i >= size) { return; } final Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) { thrownewConcurrentModificationException(); } while (i != size && modCount == expectedModCount) { consumer.accept((E) elementData[i++]); } // update once at end of iteration to reduce heap write traffic cursor = i; lastRet = i - 1; checkForComodification(); } finalvoidcheckForComodification(){ if (modCount != expectedModCount) thrownewConcurrentModificationException(); } }
其中,有三个属性:
1 2 3
int cursor; //index of next element to return int lastRet = -1; //index of last element returned; -1ifno such int expectedModCount = modCount;
@SuppressWarnings("unchecked") public E next(){ checkForComodification(); int i = cursor; if (i >= size) thrownewNoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) thrownewConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; }
publicstaticvoidmain(String[] args) { List<String> list = new ArrayList<>(); for (int i = 0 ; i < 10 ; i++ ) { list.add(i + ""); } Iterator<String> iterator = list.iterator(); int i = 0 ; while(iterator.hasNext()) { if (i == 3) { iterator.remove(); //迭代器的remove()方法 } System.out.println(iterator.next()); i ++; } }