[COLLECTIONS-476] Collection wrappers to for unmodifiable / nonnull-safe collections

• Type: New Feature
• Status: Closed
• Priority: Minor
• Resolution: Won't Fix
• Component/s: List, Set
• Assignee: Unassigned
• Reporter: offbynull
• Created: 28/Dec/12 06:20
• Updated: 27/Nov/15 21:47
• Resolved: 24/Jan/15 14:19

Description

Would it be possible to add something like this to commons lang? Commons collection looks like it's pretty much dead, and the only alternative for this kind of stuff is Google's horribly designed and massively confusing Guava library.

Below are a couple of quick and dirty (untested) examples of the kind of wrappers I'm talking about. Note the isLocked/locked methods and the viewBlacklist method. Using these methods, it's easy for a component receiving a list/set to identify that it's currently unmodifiable and that the collection restricts certain values (e.g. null? maybe others?).

public final class LockableBlacklistableList<T> implements List<T> {

    private boolean locked;
    private List<T> list;
    private Set<T> blacklist;

    public LockableBlacklistableList(List<T> backingList, T... blacklist) {
        if (backingList == null) {
            throw new NullPointerException();
        }

        if (!backingList.isEmpty()) {
            throw new IllegalArgumentException();
        }
        this.blacklist = new HashSet<>(Arrays.asList(blacklist));
        this.list = backingList;
    }

    public void lock() {
        locked = true;
    }

    public boolean isLocked() {
        return locked;
    }

    public Set<T> viewBlacklist() {
        return Collections.unmodifiableSet(blacklist);
    }

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

    @Override
    public boolean isEmpty() {
        return list.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
        return list.contains(o);
    }

    @Override
    public Iterator<T> iterator() {
        final Iterator<T> it = list.iterator();
        return new Iterator<T>() {
            @Override
            public boolean hasNext() {
                return it.hasNext();
            }

            @Override
            public T next() {
                return it.next();
            }

            @Override
            public void remove() {
                if (locked) {
                    throw new IllegalStateException();
                }
                it.remove();
            }
        };
    }

    @Override
    public Object[] toArray() {
        return list.toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
        return list.toArray(a);
    }

    @Override
    public boolean add(T e) {
        if (locked) {
            throw new IllegalStateException();
        }
        return list.add(e);
    }

    @Override
    public boolean remove(Object o) {
        if (locked) {
            throw new IllegalStateException();
        }
        return list.remove(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
        return list.containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends T> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        for (T item : c) {
            if (blacklist.contains(item)) {
                throw new IllegalArgumentException();
            }
        }
        return list.addAll(c);
    }

    @Override
    public boolean addAll(int index, Collection<? extends T> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        for (T item : c) {
            if (blacklist.contains(item)) {
                throw new IllegalArgumentException();
            }
        }
        return list.addAll(index, c);
    }

    @Override
    public boolean removeAll(Collection<?> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        return list.removeAll(c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        return list.retainAll(c);
    }

    @Override
    public void clear() {
        if (locked) {
            throw new IllegalStateException();
        }
        list.clear();
    }

    @Override
    public boolean equals(Object o) {
        return list.equals(o);
    }

    @Override
    public int hashCode() {
        return list.hashCode();
    }

    @Override
    public T get(int index) {
        return list.get(index);
    }

    @Override
    public T set(int index, T element) {
        if (locked) {
            throw new IllegalStateException();
        }
        if (blacklist.contains(element)) {
            throw new IllegalArgumentException();
        }
        return list.set(index, element);
    }

    @Override
    public void add(int index, T element) {
        if (locked) {
            throw new IllegalStateException();
        }
        if (blacklist.contains(element)) {
            throw new IllegalArgumentException();
        }
        list.add(index, element);
    }

    @Override
    public T remove(int index) {
        if (locked) {
            throw new IllegalStateException();
        }
        return list.remove(index);
    }

    @Override
    public int indexOf(Object o) {
        return list.indexOf(o);
    }

    @Override
    public int lastIndexOf(Object o) {
        return list.lastIndexOf(o);
    }

    @Override
    public ListIterator<T> listIterator() {
        final ListIterator<T> backingListIt = list.listIterator();
        return new ListIterator<T>() {
            @Override
            public boolean hasNext() {
                return backingListIt.hasNext();
            }

            @Override
            public T next() {
                return backingListIt.next();
            }

            @Override
            public boolean hasPrevious() {
                return backingListIt.hasPrevious();
            }

            @Override
            public T previous() {
                return backingListIt.previous();
            }

            @Override
            public int nextIndex() {
                return backingListIt.nextIndex();
            }

            @Override
            public int previousIndex() {
                return backingListIt.previousIndex();
            }

            @Override
            public void remove() {
                if (locked) {
                    throw new IllegalStateException();
                }
                backingListIt.remove();
            }

            @Override
            public void set(T e) {
                if (locked) {
                    throw new IllegalStateException();
                }
                if (blacklist.contains(e)) {
                    throw new IllegalArgumentException();
                }
                backingListIt.set(e);
            }

            @Override
            public void add(T e) {
                if (locked) {
                    throw new IllegalStateException();
                }
                if (blacklist.contains(e)) {
                    throw new IllegalArgumentException();
                }
                backingListIt.add(e);
            }
        };
    }

    @Override
    public ListIterator<T> listIterator(int index) {
        final ListIterator<T> backingListIt = list.listIterator(index);
        return new ListIterator<T>() {
            @Override
            public boolean hasNext() {
                return backingListIt.hasNext();
            }

            @Override
            public T next() {
                return backingListIt.next();
            }

            @Override
            public boolean hasPrevious() {
                return backingListIt.hasPrevious();
            }

            @Override
            public T previous() {
                return backingListIt.previous();
            }

            @Override
            public int nextIndex() {
                return backingListIt.nextIndex();
            }

            @Override
            public int previousIndex() {
                return backingListIt.previousIndex();
            }

            @Override
            public void remove() {
                if (locked) {
                    throw new IllegalStateException();
                }
                backingListIt.remove();
            }

            @Override
            public void set(T e) {
                if (locked) {
                    throw new IllegalStateException();
                }
                if (blacklist.contains(e)) {
                    throw new IllegalArgumentException();
                }
                backingListIt.set(e);
            }

            @Override
            public void add(T e) {
                if (locked) {
                    throw new IllegalStateException();
                }
                if (blacklist.contains(e)) {
                    throw new IllegalArgumentException();
                }
                backingListIt.add(e);
            }
        };
    }

    @Override
    public List<T> subList(int fromIndex, int toIndex) {
        LockableBlacklistableList<T> ret = new LockableBlacklistableList<>(
                list.subList(fromIndex, toIndex));
        ret.locked = locked;
        ret.blacklist = blacklist;
        return ret;
    }
}

public final class LockableBlacklistableSet<T> implements Set<T> {
    private boolean locked;
    private Set<T> set;
    private Set<T> blacklist;

    public LockableBlacklistableSet(Set<T> backingSet, T... blacklist) {
        if (backingSet == null) {
            throw new NullPointerException();
        }

        if (!backingSet.isEmpty()) {
            throw new IllegalArgumentException();
        }
        this.blacklist = new HashSet<>(Arrays.asList(blacklist));
        this.set = backingSet;
    }
    
    public void lock() {
        locked = true;
    }

    public boolean isLocked() {
        return locked;
    }

    public Set<T> viewBlacklist() {
        return Collections.unmodifiableSet(blacklist);
    }

    public int size() {
        return set.size();
    }

    public boolean isEmpty() {
        return set.isEmpty();
    }

    public boolean contains(Object o) {
        return set.contains(o);
    }

    public Iterator<T> iterator() {
        final Iterator<T> it = set.iterator();
        return new Iterator<T>() {
            @Override
            public boolean hasNext() {
                return it.hasNext();
            }

            @Override
            public T next() {
                return it.next();
            }

            @Override
            public void remove() {
                if (locked) {
                    throw new IllegalStateException();
                }
                it.remove();
            }
        };
    }

    public Object[] toArray() {
        return set.toArray();
    }

    public <T> T[] toArray(T[] a) {
        return set.toArray(a);
    }

    public boolean add(T e) {
        if (locked) {
            throw new IllegalStateException();
        }
        if (blacklist.contains(item)) {
            throw new IllegalArgumentException();
        }
        return set.add(e);
    }

    public boolean remove(Object o) {
        if (locked) {
            throw new IllegalStateException();
        }
        return set.remove(o);
    }

    public boolean containsAll(Collection<?> c) {
        return set.containsAll(c);
    }

    public boolean addAll(Collection<? extends T> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        for (T item : c) {
            if (blacklist.contains(item)) {
                throw new IllegalArgumentException();
            }
        }
        return set.addAll(c);
    }

    public boolean retainAll(Collection<?> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        return set.retainAll(c);
    }

    public boolean removeAll(Collection<?> c) {
        if (locked) {
            throw new IllegalStateException();
        }
        return set.removeAll(c);
    }

    public void clear() {
        if (locked) {
            throw new IllegalStateException();
        }
        set.clear();
    }

    public boolean equals(Object o) {
        return set.equals(o);
    }

    public int hashCode() {
        return set.hashCode();
    }
}