Map的內容按字母順序排序

map有自帶的排序功能，但需要重寫排序方法，代碼如下：

package coreJava.com.shindo.corejava.map;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class MapSort {
    /**
     * 
     * @Title: sortMap
     * @Description: 對集合內的數據按key的字母順序做排序
     */
    public List<Map.Entry<String, String>> sortMap(final Map<String, String> map) {
        final List<Map.Entry<String, String>> infos = new ArrayList<Map.Entry<String, String>>(map.entrySet());

        // 重寫集合的排序方法：按字母順序
        Collections.sort(infos, new Comparator<Map.Entry<String, String>>() {
            @Override
            public int compare(final Entry<String, String> o1, final Entry<String, String> o2) {
                return (o1.getKey().toString().compareTo(o2.getKey()));
            }
        });

        return infos;
    }

    public static void main(final String[] args) {
        final Map<String, String> map = new HashMap<String, String>();
        map.put("charSet", "utf-8");
        map.put("merId", "5412");
        map.put("acqId", "321");

        final List<Map.Entry<String, String>> list = new MapSort().sortMap(map);

        for (final Map.Entry<String, String> m : list) {
            System.out.println(m.getKey() + ":" + m.getValue());
        }

    }

}

 

執行main方法，結果如下：

acqId:321
charSet:utf-8
merId:5412