从java 9开始收集。启用过滤:

public static <T, A, R>
    Collector<T, ?, R> filtering(Predicate<? super T> predicate,
                                 Collector<? super T, A, R> downstream)

因此过滤应该是:

collection.stream().collect(Collectors.filtering(predicate, collector))

例子:

List<Integer> oddNumbers = List.of(1, 19, 15, 10, -10).stream()
            .collect(Collectors.filtering(i -> i % 2 == 1, Collectors.toList()));

我需要根据列表中已经存在的值来筛选列表。例如，删除后面小于当前值的所有值。{2 5 3 4 7 5} ->{2 5 7}。或者例如删除所有重复项{3 5 4 2 3 5 6}->{3 5 4 2 6}。

public class Filter {
    public static <T> void List(List<T> list, Chooser<T> chooser) {
        List<Integer> toBeRemoved = new ArrayList<>();
        leftloop:
        for (int right = 1; right < list.size(); ++right) {
            for (int left = 0; left < right; ++left) {
                if (toBeRemoved.contains(left)) {
                    continue;
                }
                Keep keep = chooser.choose(list.get(left), list.get(right));
                switch (keep) {
                    case LEFT:
                        toBeRemoved.add(right);
                        continue leftloop;
                    case RIGHT:
                        toBeRemoved.add(left);
                        break;
                    case NONE:
                        toBeRemoved.add(left);
                        toBeRemoved.add(right);
                        continue leftloop;
                }
            }
        }

        Collections.sort(toBeRemoved, new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o2 - o1;
            }
        });

        for (int i : toBeRemoved) {
            if (i >= 0 && i < list.size()) {
                list.remove(i);
            }
        }
    }

    public static <T> void List(List<T> list, Keeper<T> keeper) {
        Iterator<T> iterator = list.iterator();
        while (iterator.hasNext()) {
            if (!keeper.keep(iterator.next())) {
                iterator.remove();
            }
        }
    }

    public interface Keeper<E> {
        boolean keep(E obj);
    }

    public interface Chooser<E> {
        Keep choose(E left, E right);
    }

    public enum Keep {
        LEFT, RIGHT, BOTH, NONE;
    }
}

这将被这样使用。

List<String> names = new ArrayList<>();
names.add("Anders");
names.add("Stefan");
names.add("Anders");
Filter.List(names, new Filter.Chooser<String>() {
    @Override
    public Filter.Keep choose(String left, String right) {
        return left.equals(right) ? Filter.Keep.LEFT : Filter.Keep.BOTH;
    }
});

使用来自Apache Commons的CollectionUtils.filter(Collection,Predicate)。

从java 9开始收集。启用过滤:

public static <T, A, R>
    Collector<T, ?, R> filtering(Predicate<? super T> predicate,
                                 Collector<? super T, A, R> downstream)

因此过滤应该是:

collection.stream().collect(Collectors.filtering(predicate, collector))

例子:

List<Integer> oddNumbers = List.of(1, 19, 15, 10, -10).stream()
            .collect(Collectors.filtering(i -> i % 2 == 1, Collectors.toList()));

我将把RxJava加入其中，它在Android上也可用。RxJava可能并不总是最好的选择，但如果您希望在集合上添加更多转换或在过滤时处理错误，RxJava将为您提供更大的灵活性。

Observable.from(Arrays.asList(1, 2, 3, 4, 5))
    .filter(new Func1<Integer, Boolean>() {
        public Boolean call(Integer i) {
            return i % 2 != 0;
        }
    })
    .subscribe(new Action1<Integer>() {
        public void call(Integer i) {
            System.out.println(i);
        }
    });

输出:

1
3
5

更多关于RxJava过滤器的细节可以在这里找到。

https://code.google.com/p/joquery/

支持不同的可能性，

给定的集合,

Collection<Dto> testList = new ArrayList<>();

的类型,

class Dto
{
    private int id;
    private String text;

    public int getId()
    {
        return id;
    }

    public int getText()
    {
        return text;
    }
}

过滤器

Java 7

Filter<Dto> query = CQ.<Dto>filter(testList)
    .where()
    .property("id").eq().value(1);
Collection<Dto> filtered = query.list();

Java 8

Filter<Dto> query = CQ.<Dto>filter(testList)
    .where()
    .property(Dto::getId)
    .eq().value(1);
Collection<Dto> filtered = query.list();

同时,

Filter<Dto> query = CQ.<Dto>filter()
        .from(testList)
        .where()
        .property(Dto::getId).between().value(1).value(2)
        .and()
        .property(Dto::grtText).in().value(new string[]{"a","b"});

排序(也可用于Java 7)

Filter<Dto> query = CQ.<Dto>filter(testList)
        .orderBy()
        .property(Dto::getId)
        .property(Dto::getName)
    Collection<Dto> sorted = query.list();

分组(也可用于Java 7)

GroupQuery<Integer,Dto> query = CQ.<Dto,Dto>query(testList)
        .group()
        .groupBy(Dto::getId)
    Collection<Grouping<Integer,Dto>> grouped = query.list();

连接(也可用于Java 7)

考虑到,

class LeftDto
{
    private int id;
    private String text;

    public int getId()
    {
        return id;
    }

    public int getText()
    {
        return text;
    }
}

class RightDto
{
    private int id;
    private int leftId;
    private String text;

    public int getId()
    {
        return id;
    }

    public int getLeftId()
        {
            return leftId;
        }

    public int getText()
    {
        return text;
    }
}

class JoinedDto
{
    private int leftId;
    private int rightId;
    private String text;

    public JoinedDto(int leftId,int rightId,String text)
    {
        this.leftId = leftId;
        this.rightId = rightId;
        this.text = text;
    }

    public int getLeftId()
    {
        return leftId;
    }

    public int getRightId()
        {
            return rightId;
        }

    public int getText()
    {
        return text;
    }
}

Collection<LeftDto> leftList = new ArrayList<>();

Collection<RightDto> rightList = new ArrayList<>();

可以像这样连接，

Collection<JoinedDto> results = CQ.<LeftDto, LeftDto>query().from(leftList)
                .<RightDto, JoinedDto>innerJoin(CQ.<RightDto, RightDto>query().from(rightList))
                .on(LeftFyo::getId, RightDto::getLeftId)
                .transformDirect(selection ->  new JoinedDto(selection.getLeft().getText()
                                                     , selection.getLeft().getId()
                                                     , selection.getRight().getId())
                                 )
                .list();

表达式

Filter<Dto> query = CQ.<Dto>filter()
    .from(testList)
    .where()
    .exec(s -> s.getId() + 1).eq().value(2);