guava iterable example

public class IteratorTest {
    public static void main(String[] args) {
        test();
    }

    public static void test() {
        final Function<String, Iterable<String>> function = new Function<String, Iterable<String>>() {

            @Override
            public Iterable<String> apply(final String input) {
                return new Iterable<String>() {
                    @Override
                    public Iterator<String> iterator() {
                        return new AbstractIterator<String>() {
                            int start = 0;
                            int end = input.length();

                            @Override
                            protected String computeNext() {
                                if (start > end - 1) {
                                    return endOfData();
                                }
                                return String.valueOf(input.charAt(start++));
                            }
                        };
                    }
                };
            }
        };
        List<String> names = Lists.newArrayList("123", "456", "789", "abc");
        Function<List<String>, Iterable<Iterable<String>>> fun = new Function<List<String>, Iterable<Iterable<String>>>() {
            @Override
            public Iterable<Iterable<String>> apply(final List<String> input) {
                return new Iterable<Iterable<String>>() {
                    @Override
                    public Iterator<Iterable<String>> iterator() {
                        return new AbstractIterator<Iterable<String>>() {
                            int size = 0;

                            @Override
                            protected Iterable<String> computeNext() {
                                if (size > input.size() - 1) {
                                    return endOfData();
                                }
                                Iterable<String> apply = function.apply(input.get(size++));
                                Preconditions.checkNotNull(apply);
                                return apply;
                            }
                        };
                    }
                };
            }
        };
        Function<Iterable<Iterable<String>>, Iterable<String>> convert = new Function<Iterable<Iterable<String>>, Iterable<String>>() {
            @Override
            public Iterable<String> apply(final Iterable<Iterable<String>> iterators) {
                return new Iterable<String>() {
                    @Override
                    public Iterator<String> iterator() {
                        return new AbstractIterator<String>() {
                            Iterator<Iterable<String>> outerIterator = iterators.iterator();
                            Iterator<String> innerIterator = null;

                            @Override
                            protected String computeNext() {
                                if (innerIterator == null) {
                                    if (!outerIterator.hasNext()) {
                                        return endOfData();
                                    }
                                    innerIterator = outerIterator.next().iterator();
                                }
                                while (innerIterator.hasNext()) {
                                    return innerIterator.next();
                                }
                                innerIterator = null;
                                return computeNext();
                            }
                        };
                    }
                };
            }
        };
        //每次外部的iterator便利一次就回不去了，所以为了每次获取到都是从0开始的，需要包一层
        Function<Iterator<String>, Iterable<String>> con = new Function<Iterator<String>, Iterable<String>>() {
            @Override
            public Iterable<String> apply(final Iterator<String> input) {
                return new Iterable<String>() {
                    @Override
                    public Iterator<String> iterator() {
                        return new AbstractIterator<String>() {
                            Iterator<String> inner = input;

                            @Override
                            protected String computeNext() {
                                while (inner.hasNext()) {
                                    return inner.next();
                                }
                                return endOfData();
                            }
                        };
                    }
                };
            }
        };
        Iterable<Iterable<String>> res = fun.apply(names);
        Iterable<String> iterators = convert.apply(res);
        for(String name:iterators){
            System.out.println(name);
        }
        System.out.println(Iterables.size(iterators));
        //直接转换
        Iterables.concat(res);

    }

    public void test2() {
        Function<String, Iterable<String>> function = new Function<String, Iterable<String>>() {

            @Override
            public Iterable<String> apply(final String input) {
                return new Iterable<String>() {
                    @Override
                    public Iterator<String> iterator() {
                        return new AbstractIterator<String>() {
                            int start = 0;
                            int end = input.length();

                            @Override
                            protected String computeNext() {
                                if (start > end - 1) {
                                    return endOfData();
                                }
                                return String.valueOf(input.charAt(start++));
                            }
                        };
                    }
                };
            }
        };
        Iterable<String> aa = function.apply("12345");
        Preconditions.checkNotNull(aa);
        for (String a : aa) {
            System.out.println(a);
        }
        Iterable<String> bb = Iterables.filter(aa, new Predicate<String>() {
            @Override
            public boolean apply(String input) {
                return !StringUtils.equals(input, "5");
            }
        });
        Iterable<String> cc = Iterables.concat(aa, bb);
        Preconditions.checkNotNull(cc);
    }

}

　　

转载于:https://www.cnblogs.com/wscit/p/6430516.html