Map.Entry重定义，用于2维映射的迭代器 [英] Map.Entry redefinition, for iterator of 2 Dimensional Map

问题描述

我们有一个功课来实现一个类，它创建一个将成为字符串二维图的对象。 centralMap = new HashMap< String，Map< String，String>> 。教授给了我们一个接口，其中包含我们应该重新定义的方法，比如put方法（ public String put（final String row，final String column，final String value） ）get方法（ public String get（final String row，final String column））和其他一些方法..以及我无法重新定义的方法，是迭代器方法..在他给出的界面中，有一个类Entry，他说，我们只将其用于迭代器方法！但我不知道我们应该怎么做..这是类Entry，以及我们应该重新定义（实现）的迭代器方法：

We have a homework, to implement a class, that creates an Object that will be a 2Dimensional Map of Strings. centralMap = new HashMap<String, Map<String,String>>. The professor gave us an interface, that contains the methods that we should redefine, like the put method (public String put(final String row, final String column, final String value)) the get method (public String get(final String row, final String column)) and some other methods.. and the one that i couldn't redefine, is the iterator method.. In the interface that he gave, there was a class Entry, that he said, we ll use it just for the iterator method! But I have no idea what should we do with it.. Here is the class Entry, and the iterator method that we should redefine(implement):

final class Entry
{
    /** First Key. */
    private final String key1;

    /** Second Key. */
    private final String key2;

    /** Value. */
    private final String value;

    /** Cponstructor for a new Tripel.
     * @param key1 First Key.
     * @param key2 Second Key.
     * @param value Value.
     */
    public Entry(final String key1, final String key2, final String value)
    {
        this.key1 = key1;
        this.key2 = key2;
        this.value = value;
    }

    public String getFirstKey()
    {
        return key1;
    }

    public String getSecondKey()
    {
        return key2;
    }

    public String getValue()
    {
        return value;
    }

    @Override public boolean equals(final Object anything)
    {
        if(anything == null)
            return false;
        if(getClass() != anything.getClass())
            return false;
        final Entry that = (Entry)anything;
        return Objects.equals(getFirstKey(), that.getFirstKey())
               && Objects.equals(getSecondKey(), that.getSecondKey())
               && Objects.equals(getValue(), that.getValue());
    }

    // CHECKSTYLE- Magic Number
    @Override public int hashCode()
    {
        int hash = 7;
        hash = 17 * hash + Objects.hashCode(getFirstKey());
        hash = 17 * hash + Objects.hashCode(getSecondKey());
        hash = 17 * hash + Objects.hashCode(getValue());
        return hash;
    }
    // CHECKSTYLE+ Magic Number

    @Override public String toString()
    {
        return String.format("(%s, %s, %s)", getFirstKey(), getSecondKey(), getValue());
    }

}

以及我们应该使用的迭代器方法重新定义是这个： @Override Iterator< Entry> iterator（）; 我该怎么办？我听说我们应该为迭代器实现一个新类..
告诉我你是否需要我实现的类，（并实现他给出的接口）知道我如何将嵌套映射放在另一个一个等等..因为嵌套的地图刚刚在put方法中创建..在我的构造函数中只有centralMap。

and the iterator method that we should redefine is this one: @Override Iterator<Entry> iterator(); How should I proceed? I heard that we should implement a new class just for the iterator.. tell me if you need the class that I implemented, (and which implements the interface he gave) to know how i put the nested map in the other one etc.. because the nested map is just created in the put method.. in my constructor there s just the centralMap.

非常感谢你的帮助!!

Thanks a lot for your help!!

推荐答案

你只需要必须创建一个方法，创建一个 Iterator 条目。由于使用了地图，每个条目都是唯一的。所以你只需要执行以下操作：

You simply have to create an method, that creates an Iterator of entries. Every Entry is unique, because of the used Maps. So you just need to do something like:

for entryMap in map do {
  entryMap get list of keysAndValues
  for keyValue in keysAndValues preppend this key
}

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