java -- 對Map按鍵排序、按值排序

　　　　　　　　　　　　　　　　　　　　　　　　　　　　                         java  -- 對Map按鍵、按值排序

 

1.按鍵排序(sort by key)

    直接上代碼  ↓

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)

    按值排序就相對麻煩些了，沒有直接可用的數據結構能處理相似需求，須要咱們本身轉換一下。

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. 後記

    若是map存儲的是<String,對象>類型的數據 可讓對象實現java.lang.Comparable<>接口，並按照你本身的排序規則重寫compareTo方法！