Map值按key排序或是按 value排序

来源：互联网发布：2017数据录入员工资编辑：程序博客网时间：2024/06/06 01:55

实现Map的按值Value（非Key）排序

Map<String, Integer> map = new TreeMap<String, Integer>();

map.put("j2se", 20);
map.put("j2ee", 10);
map.put("j2me", 30);

List<Map.Entry<String, Integer>> infoIds = new ArrayList<Map.Entry<String, Integer>>(
map.entrySet());
//排序前
for (int i = 0; i < infoIds.size(); i++) {
String id = infoIds.get(i).toString();
System.out.println(id);
}
//排序
Collections.sort(infoIds, new Comparator<Map.Entry<String, Integer>>() {
public int compare(Map.Entry<String, Integer> o1,
Map.Entry<String, Integer> o2) {
return (o2.getValue() - o1.getValue());
}
});
//排序后
for (int i = 0; i < infoIds.size(); i++) {
String id = infoIds.get(i).toString();
System.out.println(id);
}
排序前：
j2ee=10
j2me=30
j2se=20
排序后：
j2me=30
j2se=20
j2ee=10

实现Map的按值Value（非Key）排序

public static String getSignData(Map<String, String> params)
    {
        StringBuffer content = new StringBuffer();

        // 按照key做排序
        List<String> keys = new ArrayList<String>(params.keySet());
        Collections.sort(keys);
        for (int i = 0; i < keys.size(); i++)
        {
            String key = (String) keys.get(i);
            if ("sign".equals(key))//代替一下
            {
                continue;
            }
            String value = (String) params.get(key);
            if (value != null)
            {
                content.append((i == 0 ? "" : "&") + key + "=" + value);
            }
            else
            {
               continue;
            }
        }
        return content.toString();
    }