Java對List(Date,String,int)對象進行排序工具類

有時候須要對List對象進行排序,若是每一處都去寫一個排序方法,就會產生重複代碼的壞味道,並且每一處都寫,工做量會很大。 咱們知道,Java提供了一個Collections.sort()方法能夠對List排序,利用Java反射機制,很容易就能寫出一個通用的排序方法。ide

爲了防止出現不按照getter,setter規範命名的POJO類,我不打算動態調用getXXX()方法,而是直接獲取對象的屬性值。爲了達到不管是否是public成員變量,都能獲取到的目的,在獲取到Field後,調用了setAccessible(true); 來設置訪問權限。 具體代碼以下:.net

/**code

  • 對List對象按照某個成員變量進行排序對象

  • @param list List對象blog

  • @param sortField 排序的屬性名稱排序

  • @param sortMode 排序方式:ASC,DESC 任選其一 */
    public static <T> void sortList(List<T> list, final String sortField, final String sortMode) {
    if(list == null || list.size() < 2) {
    return;
    }
    Collections.sort(list, new Comparator<T>() {
    @Override
    public int compare(T o1, T o2) {
    try {
    Class clazz = o1.getClass();
    Field field = clazz.getDeclaredField(sortField); //獲取成員變量
    field.setAccessible(true); //設置成可訪問狀態
    String typeName = field.getType().getName().toLowerCase(); //轉換成小寫get

    Object v1 = field.get(o1); //獲取field的值  
             Object v2 = field.get(o2); //獲取field的值  
    
             boolean ASC_order = (sortMode == null || "ASC".equalsIgnoreCase(sortMode));  
    
             //判斷字段數據類型,並比較大小  
             if(typeName.endsWith("string")) {  
                 String value1 = v1.toString();  
                 String value2 = v2.toString();  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("short")) {  
                 Short value1 = Short.parseShort(v1.toString());  
                 Short value2 = Short.parseShort(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("byte")) {  
                 Byte value1 = Byte.parseByte(v1.toString());  
                 Byte value2 = Byte.parseByte(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("char")) {  
                 Integer value1 = (int)(v1.toString().charAt(0));  
                 Integer value2 = (int)(v2.toString().charAt(0));  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("int") || typeName.endsWith("integer")) {  
                 Integer value1 = Integer.parseInt(v1.toString());  
                 Integer value2 = Integer.parseInt(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("long")) {  
                 Long value1 = Long.parseLong(v1.toString());  
                 Long value2 = Long.parseLong(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("float")) {  
                 Float value1 = Float.parseFloat(v1.toString());  
                 Float value2 = Float.parseFloat(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("double")) {  
                 Double value1 = Double.parseDouble(v1.toString());  
                 Double value2 = Double.parseDouble(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("boolean")) {  
                 Boolean value1 = Boolean.parseBoolean(v1.toString());  
                 Boolean value2 = Boolean.parseBoolean(v2.toString());  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("date")) {  
                 Date value1 = (Date)(v1);  
                 Date value2 = (Date)(v2);  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else if(typeName.endsWith("timestamp")) {  
                 Timestamp value1 = (Timestamp)(v1);  
                 Timestamp value2 = (Timestamp)(v2);  
                 return ASC_order ? value1.compareTo(value2) : value2.compareTo(value1);  
             }  
             else {  
                 //調用對象的compareTo()方法比較大小  
                 Method method = field.getType().getDeclaredMethod("compareTo", new Class[]{field.getType()});  
                 method.setAccessible(true); //設置可訪問權限  
                 int result  = (Integer)method.invoke(v1, new Object[]{v2});  
                 return ASC_order ? result : result*(-1);  
             }  
         }  
         catch (Exception e) {  
             String err = e.getLocalizedMessage();  
             System.out.println(err);  
             e.printStackTrace();  
         }  
    
         return 0; //未知類型,沒法比較大小  
     }

    });
    }string

轉自:http://blog.csdn.net/zht666/article/details/16989329it

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