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。
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:java
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ide
- /**
- * 對List對象按照某個成員變量進行排序
- * @param list List對象
- * @param sortField 排序的屬性名稱
- * @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) {
- 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
-
- 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
- }
- });
- }
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