java - 根据另一个类中可用的参数对列表进行排序

Answer 1

你可以使用一些闻起来像高阶函数的东西。也就是说，创建一个静态函数，该函数采用从 Long 到 int（这是优先级）或数据的排序映射并返回一个新的比较器。

Foo 类有一个getComparator采用 Orange 的静态方法。Orange 是一个类，它有一个方法，该方法getPriority接受一个 ID 并返回相应的优先级。该getComparator方法构造一个新Comparator对象。新Comparator对象的compare方法采用两个 ID。它查找两个 ID 的相应优先级并进行比较。

public interface Orange {
    // Looks up id and returns the corresponding Priority.
    public int getPriority(Long id);
}

public class Foo {
    public static Comparator<Long> getComparator(final Orange orange) {
        return new Comparator<Long>() {
            public int compare(Long id1, Long id2) {
                // Get priority through orange, or
                // Make orange juice from our orange.
                // You may want to compare them in a different way.
                return orange.getPriority(id1) - orange.getPriority(id2);
        };
    }
}

我的 java 有点生锈，所以代码可能有缺陷。不过，总体思路应该可行。

用法：

// This is defined somewhere. It could be a local variable or an instance
// field or whatever. There's no exception (except is has to be in scope).
Collection c = ...;
...
Orange orange = new Orange() {
    public int getPriority(Long id) {
        // Insert code that searches c.mySet for an instance of data
        // with the desired ID and return its Priority
    }
};
Collections.sort(c.myList, Foo.getComparator(orange));

我没有举例说明橙色的外观。

Answer 2

我假设你有一个List<Data>存储在某个地方。在比较器中，你需要getDataById从你的数据类中调用一个方法，并通过优先级排序。

检查下面的代码..我已将单个类用于多种目的..

理想情况下，您希望将其分解为更多类..但这只是一个演示，如何实现您想要的..

class Container {
    // List of Data  instances created..
    // This list has to be static, as it is for a class, 
    // and not `instance specific`
    public static List<Data> dataList = new ArrayList<Data>();

    // List of Ids, that you want to sort.
    private List<Long> idList = new ArrayList<Long>();

    // Populate both the list..

    // Have a method that will iterate through static list to 
    // find Data instance for a particular id

    public static Data getDataById(long id) {
        // Find Data with id from the list

        // Return Data
    }

    public void sortList() {
        Collections.sort(idList, new MyComparator());
    }
}

public MyComparator implements Comparator<Long> {

    public int compare(Long int1, Long int2) {
        Data data1 = Container.getDataById(int1);
        Data data2 = Container.getDataById(int2);

        return data1.getPriority() - data2.getPriority();
    }
}