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