如何对HashMap进行排序<String, String[]>通过 android 中的字符串 [英] How to sort HashMap&lt;String, String[]&gt; by String in android

问题描述

我有这个代码:

    HashMap<String, String[]> unsorted = new HashMap<String, String[]>();
    String[] values = new String[3];
    String key;

    //add data to hashmap
    key = "abc";
    values[0] = "a"; values[1]="b"; values[2]="c";
    unsorted.put(key, values);

    key = "abc";
    values[0] = "aa"; values[1]="bb"; values[2]="cb";
    unsorted.put(key, values);

    key = "def";
    values[0] = "d"; values[1]="e"; values[2]="f";
    unsorted.put(key, values);

    //sort hashmap
    /***********/

    //output should be:
    { abc-[a,b,c], abc-[aa,bb,cc], def-[d,e,f] }

    //or

    { abc-[aa,bb,cc], abc-[a,b,c], def-[d,e,f] }

我怎么能这样排序?注意:我尝试使用 TreeMap 和其他示例，但它们消除了 键 相等的元素.

How can I sort it like that? Note: I tried with using TreeMap, and other examples, but they eliminate the elements where the keys are equal.

我解决了我的问题 :) 感谢 Guillaume.这是我使用的:

I solved my problem :) thanks to Guillaume. Here is what I used:

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

public class test {

public static void main(String[] args) {

    ArrayList<CustomObject> objs = new ArrayList<CustomObject>();

    objs.add(new CustomObject("abc", new String[] {"a", "b", "c"}));
    objs.add(new CustomObject("def", new String[] {"d", "e", "f"}));
    objs.add(new CustomObject("abc", new String[] {"aa", "bb", "cc"}));


    System.out.println(objs.isEmpty());

    Collections.sort(objs, new Comparator<CustomObject>() {
        @Override
        public int compare(CustomObject o1, CustomObject o2) {
            int i = o1.getKey().compareTo(o2.getKey());
            if(i == 0)
                return -1;
            return i;
        }
    });

    for(int i=0; i<objs.size(); i++)
        System.out.println("key/value pair:" + objs.get(i).getKey() + " - " + objs.get(i).getValues()[0]);
    }
}

和自定义对象:

public class CustomObject {

private String key;
private String[] values;

public CustomObject(String key, String[] values) {
    this.key = key;
    this.values = values;
}

public String getKey() {
    return key;
}

public String[] getValues() {
    return values;
}
}

推荐答案

如果您需要特殊的排序，并且能够拥有多个具有相同键"的对象，那对于List 来说是一种尖叫，使用自定义 Comparator.

If you need special ordering, and the ability to have multiple objects that have an equal "key", that screams for List, with a custom Comparator.

1- 定义要存储在列表中的元素类.在您的情况下，它是一个具有 2 个字段的对象:一个键"和一个字符串数组.我们称之为CustomObject(你可以随意调用)

1- Define a class of elements to store in your list. In your case, it's an object that has 2 fields: a "key" and an array of String. Let's call it CustomObject (you can call it as you like)

2- 把你所有的物品都放在列表中

2- Stick all your objects in the list

像这样:

list.add(new CustomObject("abc", new String[] {"a", "b", "c"});
list.add(new CustomObject("abc", new String[] {"aa", "bb", "cc"});
list.add(new CustomObject("def", new String[] {"d", "e", "f"});

3- 使用自定义比较器对您的列表进行排序.

3- Order your list using a custom comparator.

要对列表进行排序，请执行

To order the list do

Collections.sort(list, new Comparator<CustomObject>() {
        @Override
        public int compare(CustomObject o1, CustomObject o2) {
            return o1.getArray().compare(o2.getArray());
        }
    });

(您的比较器需要更复杂一些，才能正确比较数组，但您明白我的意思).

(your comparator needs to be a bit more sophisticated, to properly compare arrays, but you see my point).

另一种方法是将自然顺序添加到您的 CustomObject(实现 Comparable)，并将它们粘贴到 TreeSet 中.

An alternative to that is to add a natural ordering to your CustomObject (implements Comparable), and stick them into a TreeSet.

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