list<T>排序及思考

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排序工具类：

import java.lang.reflect.Field;import java.lang.reflect.Method;import java.sql.Timestamp;import java.util.Collections;import java.util.Comparator;import java.util.Date;import java.util.List;public class ListUtils {/**  * 对List对象按照某个成员变量进行排序  * @param list       List对象  * @param sortField  排序的属性名称  * @param sortMode   排序方式：ASC，DESC 任选其一  */  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); //获取成员变量                  field.setAccessible(true); //设置成可访问状态                  String typeName = field.getType().getName().toLowerCase(); //转换成小写                  Object v1 = field.get(o1); //获取field的值                  Object v2 = field.get(o2); //获取field的值                    boolean ASC_order = (sortMode == null || "ASC".equalsIgnoreCase(sortMode));                    //判断字段数据类型，并比较大小                  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 {                      //调用对象的compareTo()方法比较大小                      Method method = field.getType().getDeclaredMethod("compareTo", new Class[]{field.getType()});                      method.setAccessible(true); //设置可访问权限                      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; //未知类型，无法比较大小          }      });  }  }

以上排序不做过多说明。

List<T>正好解决一个需求：两个List<A>、List<B>，实体A和B有相同的两个或多个字段a，b，c等，我需要对这些字段的值进行相同的处理。

List<A>和List<B>用List<T>抽象出来，然后用反射对T取值赋值。

下边是反射取值赋值的代码：

public <T> List<T> covertRangeTest(List<T> list, String ghdm)throws GhglException, IllegalArgumentException,IllegalAccessException, NoSuchFieldException, SecurityException,InstantiationException {for (int i = 0; i < list.size(); i++) {T o = list.get(i);Class clazz = o.getClass();Field field = clazz.getDeclaredField("zgrs"); // 获取成员变量field.setAccessible(true); // 设置成可访问状态long zgrsValue = (long) field.get(o); // 获取field的值Field rsRange = clazz.getDeclaredField("rsRange");// 获取字段rsRange.setAccessible(true); // 设置成可访问状态rsRange.set(o, "0-9人");// 为字段赋值}return list;}

java反射详解

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