java -- 对Map按键排序、按值排序

　　　　　　　　　　　　　　　　　　　　　　　　　　　　                         java  -- 对Map按键、按值排序

1.按键排序(sort by key)

直接上代码  ↓

public Map<String, String> sortMapByKey(Map<String, String> oriMap) {
    if (oriMap == null || oriMap.isEmpty()) {
        return null;
    }
    Map<String, String> sortedMap = new TreeMap<String, String>(new Comparator<String>() {
        public int compare(String key1, String key2) {
            int intKey1 = 0, intKey2 = 0;
            try {
                intKey1 = getInt(key1);
                intKey2 = getInt(key2);
            } catch (Exception e) {
                intKey1 = 0;
                intKey2 = 0;
            }
            return intKey1 - intKey2;
        }});
    sortedMap.putAll(oriMap);
    return sortedMap;
}  

private int getInt(String str) {
    int i = 0;
    try {
        Pattern p = Pattern.compile("^\\d+");
        Matcher m = p.matcher(str);
        if (m.find()) {
            i = Integer.valueOf(m.group());
        }
    } catch (NumberFormatException e) {
        e.printStackTrace();
    }
    return i;
}  

2.按值排序(sort by value)

按值排序就相对麻烦些了，没有直接可用的数据结构能处理类似需求，需要我们自己转换一下。

public Map<String, String> sortMapByValue(Map<String, String> oriMap) {
    Map<String, String> sortedMap = new LinkedHashMap<String, String>();
    if (oriMap != null && !oriMap.isEmpty()) {
        List<Map.Entry<String, String>> entryList = new ArrayList<Map.Entry<String, String>>(oriMap.entrySet());
        Collections.sort(entryList,
                new Comparator<Map.Entry<String, String>>() {
                    public int compare(Entry<String, String> entry1,
                            Entry<String, String> entry2) {
                        int value1 = 0, value2 = 0;
                        try {
                            value1 = getInt(entry1.getValue());
                            value2 = getInt(entry2.getValue());
                        } catch (NumberFormatException e) {
                            value1 = 0;
                            value2 = 0;
                        }
                        return value2 - value1;
                    }
                });
        Iterator<Map.Entry<String, String>> iter = entryList.iterator();
        Map.Entry<String, String> tmpEntry = null;
        while (iter.hasNext()) {
            tmpEntry = iter.next();
            sortedMap.put(tmpEntry.getKey(), tmpEntry.getValue());
        }
    }
    return sortedMap;
}  

3. 后记

如果map存储的是<String,对象>类型的数据 可以让对象实现java.lang.Comparable<>接口，并按照你自己的排序规则重写compareTo方法！