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alvoro
Asked:2020-05-10 02:56:14 +0000 UTC2020-05-10 02:56:14 +0000 UTC

创建一个实体类和一个负责处理一组实体的类

  • 772

从java到你，所以问题可能是微不足道的。有两个类 -Something和SomethingGroup。受到以下事实的启发：在 android-framework 中，它ViewGroup继承自以及将混合和存储在一个列表中View的便利性，直接继承自：SomethingSomethingGroupSomethingGroupSomething

class Something {
    private String name;
    private int count;

    public Something(String name, int count) {
        this.name = name;
        this.count = count;
    }

    public int getCount() {
        return count;
    }
}

class SomethingGroup extends Someting {
    private String name;
    ArrayList<Something> children;

    SomethingGroup(String name, Something ... children) {
        // super(и вот что ему сюда передать?)
        this.name = name;
        this.children = new ArrayList<>(Arrays.asList(children));
    }

    public int getCount() {
        int count = 0;
        for(Something s : children) {
            count += s.getCount();
        }
        return count;
    }
}

问题出在财产count上。在创建对象Something时，我们知道它的值，可以直接将其传递给构造函数，而在创建SomethingGroup这个值时，这个值是“间接”传递的，必须进行计算。在这种情况下如何行事？

java

2 个回答

  1. 解决了这样的问题：

    class SomethingGroup extends Something {
    private String name;
    private ArrayList<Something> children;

    SomethingGroup(String name, Something ... children) {
        super(name, getCountFrom(new ArrayList<Something>(Arrays.asList(children))));
        this.children = new ArrayList<>(Arrays.asList(children));
    }

    public int getCount() {
        return getCountFrom(this.children);
    }

    private static int getCountFrom(ArrayList<Something> children) {
        int count = 0;
        for(Something s : children) {
            count += s.getCount();
        }
        return count;
    }
}

    想不出更好的了

    • 2
  2. Best Answer

    如果您使用的是 Java 8，那么您可以更清楚地描述您的解决方案： 

        class SomethingGroup extends Something {
        private String name;
        private ArrayList<Something> children;

        SomethingGroup(String name, Something... children) {
            super(name, Stream.of(children).mapToInt(Something::getCount).sum());
            this.children = new ArrayList<>(Arrays.asList(children));
        }

        public int getCount() {
            return this.children.stream().mapToInt(Something::getCount).sum();
        }
    }
    • 2

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