Example usage for java.util Iterator Iterator

Introduction

In this page you can find the example usage for java.util Iterator Iterator.

Prototype

Iterator

Source Link

Usage

From source file:Main.java

public static Iterable<String> iterate(Matcher matcher) {
    return new Iterable<String>() {
        @Override//  www.  j a v a2s  .  c  o m
        public Iterator<String> iterator() {
            return new Iterator<String>() {
                @Override
                public boolean hasNext() {
                    return matcher.find();
                }

                @Override
                public String next() {
                    return matcher.group();
                }
            };
        }

        @Override
        public void forEach(Consumer<? super String> action) {
            while (matcher.find()) {
                action.accept(matcher.group());
            }
        }
    };
}

From source file:Main.java

static <T> Iterator<T> cycle(final Iterable<T> iterable) {
    return new Iterator<T>() {
        Iterator<T> iterator = Collections.<T>emptySet().iterator();

        @Override// w w w  .j  a  v a  2 s . co  m
        public boolean hasNext() {
            return true;
        }

        @Override
        public T next() {
            if (!iterator.hasNext()) {
                iterator = iterable.iterator();
            }
            return iterator.next();
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    };
}

From source file:Main.java

/**
 * Converts a w3c DOM nodelist into an iterator.
 * @param nl the node list//  w  w  w.j  a  v  a2 s.  c  om
 * @return the iterator wrapping the list of DOM nodes
 */
public static Iterator nodeList2Iterator(final NodeList nl) {
    final int[] i = new int[] { 0 };
    return new Iterator() {
        public boolean hasNext() {
            return i[0] < nl.getLength();
        }

        public Object next() {
            return nl.item(i[0]++);
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    };
}

From source file:Main.java

public static <T1, T2> Collection<T2> lazyMap(final Collection<T1> lst, final Function<T1, T2> mapper) {
    return new AbstractCollection<T2>() {
        @Override//from w  w  w.  jav a  2s  .c om
        public Iterator<T2> iterator() {
            return new Iterator<T2>() {
                Iterator<T1> impl = lst.iterator();

                @Override
                public boolean hasNext() {
                    return impl.hasNext();
                }

                @Override
                public T2 next() {
                    return mapper.apply(impl.next());
                }

                @Override
                public void remove() {
                    impl.remove();
                }
            };
        }

        @Override
        public int size() {
            return lst.size();
        }
    };
}

From source file:Main.java

public static <T> Iterable<T> reverse(final List<T> list) {
    return new Iterable<T>() {
        public Iterator<T> iterator() {
            final ListIterator<T> listIterator = list.listIterator(list.size());

            return new Iterator<T>() {
                public boolean hasNext() {
                    return listIterator.hasPrevious();
                }/*from w ww  . j  ava  2 s .c om*/

                public T next() {
                    return listIterator.previous();
                }

                public void remove() {
                    listIterator.remove();
                }
            };
        }
    };
}

From source file:Main.java

/**
 * @param value value to return on each iteration
 * @param n specifies how often the value is repeated
 * @return iterable returning n times the passed in value
 *//*from  ww w .  j  ava2  s. c o m*/
@SuppressWarnings("unchecked")
public static <T> Iterable<T> repeat(T value, int n) {
    if (value == null) {
        return NULL_REPEATABLE;
    }

    return () -> new Iterator() {
        private int count = 0;

        @Override
        public boolean hasNext() {
            return n < 0 || count < n;
        }

        @Override
        public Object next() {
            count++;
            return value;
        }
    };
}

From source file:Main.java

public static <T> Iterable<T> concat(final List<Iterable<? extends T>> iterables) {
    return new Iterable<T>() {
        public Iterator<T> iterator() {
            return new Iterator<T>() {
                Iterator<? extends T> iter;
                int pos = 0;

                public boolean hasNext() {
                    while (pos < iterables.size()) {
                        if (iter == null)
                            iter = iterables.get(pos).iterator();
                        if (iter.hasNext())
                            return true;
                        iter = null;/*  w  w  w  . java 2s .c  o  m*/
                        pos++;
                    }
                    return false;
                }

                public T next() {
                    while (pos < iterables.size()) {
                        if (iter == null)
                            iter = iterables.get(pos).iterator();
                        if (iter.hasNext())
                            return iter.next();
                        iter = null;
                        pos++;
                    }
                    throw new NoSuchElementException();
                }

                public void remove() {
                    throw new UnsupportedOperationException("remove");
                }
            };
        }
    };
}

From source file:Main.java

public static <T> Iterator<T> singletonIterator(final T item) {
    return new Iterator<T>() {
        private boolean gotItem = false;

        public boolean hasNext() {
            return !this.gotItem;
        }// w  w w .j a v a2s  . co  m

        public T next() {
            if (this.gotItem) {
                throw new NoSuchElementException();
            }
            this.gotItem = true;
            return item;
        }

        public void remove() {
            if (!this.gotItem) {
                this.gotItem = true;
            } else {
                throw new NoSuchElementException();
            }
        }
    };
}

From source file:Main.java

public static <T> Iterator<T> iteratorUnion(final Iterator<T>[] iterators) {
    return new Iterator<T>() {
        private int iteratorIndex = 0;
        private Iterator<T> current = iterators.length > 0 ? iterators[0] : null;

        public boolean hasNext() {
            for (;;) {
                if (current == null) {
                    return false;
                }//from ww w.  j ava 2s  .c  o  m
                if (current.hasNext()) {
                    return true;
                }
                iteratorIndex++;
                current = iteratorIndex >= iterators.length ? null : iterators[iteratorIndex];
            }
        }

        public T next() {
            for (;;) {
                if (this.current == null) {
                    throw new NoSuchElementException();
                }
                try {
                    return this.current.next();
                } catch (final NoSuchElementException nse) {
                    this.iteratorIndex++;
                    this.current = this.iteratorIndex >= iterators.length ? null
                            : iterators[this.iteratorIndex];
                }
            }
        }

        public void remove() {
            if (this.current == null) {
                throw new NoSuchElementException();
            }
            this.current.remove();
        }
    };
}

From source file:com.px100systems.util.SpringELCtx.java

/**
 * First element of anything iterable including arrays
 * @param list the list//from   w w w.  j a v a  2  s .c  o m
 * @return the first element or null
 */
@SuppressWarnings("unchecked")
public static Object firstElement(Object list) {
    if (list == null)
        return null;

    if (list instanceof Iterator) {
        Iterator<Object> l = (Iterator<Object>) list;
        return l.hasNext() ? l.next() : null;
    }

    if (list instanceof Collection) {
        Collection<Object> l = (Collection<Object>) list;
        if (l.isEmpty())
            return null;

        return firstElement(l.iterator().next());
    }

    if (list instanceof Object[]) {
        Object[] l = (Object[]) list;
        if (l.length == 0)
            return null;

        return firstElement(l[0]);
    }

    return list;
}