Question

我有这堂课：

public class SimpleEntity {
    private String id;
    private String name;
    private boolean closed;
    private List<SimpleEntity > simpleEntityChildren;
}

我希望以递归方式迭代到SimpleEntityChildren，直到最后一个元素，我不知道如何实现它。

public void iterator(SimpleEntity simpleEntity ){
    simpleEntity .forEach(entity-> {
        if(!entity.getSimpleEntityChildren.isEmpty()){
            entity.forEach(secondEntity-> {
                if(!secondEntity.getSimpleEntityChildren.isEmpty()){
                    //and so on to the last element
                }
            });
        }
    });
}

Answer 1

进行递归通话：

public void iterate(SimpleEntity entity) {
    // you might want to add some logic here, that actually does something
    // with the current SimpleEntity instance you are iterating over
    for (SimpleEntity child : entity.getSimpleEntityChildren()) {
        iterate(child);
    }
}

请注意，如果所有StackOverflowError个实例的图表中都有循环，则会导致无限递归和SimpleEntity。

正如Boris评论的那样，您可以传递方法a Consumer<SimpleEntity>，其中包含要在每个SimpleEntity实例上执行的逻辑。

public void iterate(SimpleEntity entity, Consumer<SimpleEntity> consumer) {
    consumer.accept(entity);
    for (SimpleEntity child : entity.getSimpleEntityChildren()) {
        iterate(child,consumer);
    }
}

例如，您可以递归方式打印给定SimpleEntity实例的层次结构中所有SimpleEntity个实例的名称：

SimpleEntity someEntity = ...
iterate(someEntity, e -> System.out.println(e.getName()));

您还可以添加非递归方法来启动迭代过程：

public void iterate(Consumer<SimpleEntity> consumer) {
    iterate(this,consumer);
}

现在你可以写：

SimpleEntity someEntity = ...
someEntity.iterate(e -> System.out.println(e.getName()));

Answer 2

您可以使用递归方法。

public void iterator(SimpleEntity simpleEntity ){
 simpleEntity .forEach(entity-> {        
        iterator(entity);        
  });
}

Answer 3

最佳方法是：
1. 将您的主班级更改为：

public class SimpleEntity {
    private String id;
    private String name;
    private boolean closed;
    private List<SimpleEntity > simpleEntityChildren;

    public Stream<Tree> flattened() {
        return Stream.concat(
                Stream.of(this),
                simpleEntityChildren.stream().flatMap(Tree::flattened));
    }
}

2. 然后简单地迭代它：

public void iterator(SimpleEntity simpleEntity) {
        simpleEntity.flattened().forEach(entity->{
            // Do whatever you want
        });
    }

迭代集合中的集合直到Java中的最后一个元素

3 个答案: