本工具類為按對象屬性排序工具類,實現的功能:
1.按對象的一個屬性和多個屬性進行排序.
2.按對象屬性正序和倒序排列.
3.完美支持int等基礎類和Integer等包裝類.
4.完美支持屬性為實現了Comparable接口的類.
5.如果類不是java.lang中定義的基礎類型也沒有實現Comparable接口則轉為String後進行排序.
實現思路:使用反射取得對象屬性或對象方法的值從而解除對具體對象的依賴.
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;
/**
* 通用工具類之按對象中某屬性排序
* @author 李坤
* 交流博客:http://blog.csdn.net/lk_blog
*/
public class SortListUtil {
public static final String DESC = "desc";
public static final String ASC = "asc";
/**
* 對list中的元素按升序排列.
*
* @param list
* 排序集合
* @param field
* 排序字段
* @return
*/
public static List<?> sort(List<?> list, final String field) {
return sort(list, field, null);
}
/**
* 對list中的元素進行排序.
*
* @param list
* 排序集合
* @param field
* 排序字段
* @param sort
* 排序方式: SortList.DESC(降序) SortList.ASC(升序).
* @return
*/
@SuppressWarnings("unchecked")
public static List<?> sort(List<?> list, final String field,
final String sort) {
Collections.sort(list, new Comparator() {
public int compare(Object a, Object b) {
int ret = 0;
try {
Field f = a.getClass().getDeclaredField(field);
f.setAccessible(true);
Class<?> type = f.getType();
if (type == int.class) {
ret = ((Integer) f.getInt(a)).compareTo((Integer) f
.getInt(b));
} else if (type == double.class) {
ret = ((Double) f.getDouble(a)).compareTo((Double) f
.getDouble(b));
} else if (type == long.class) {
ret = ((Long) f.getLong(a)).compareTo((Long) f
.getLong(b));
} else if (type == float.class) {
ret = ((Float) f.getFloat(a)).compareTo((Float) f
.getFloat(b));
} else if (type == Date.class) {
ret = ((Date) f.get(a)).compareTo((Date) f.get(b));
} else if (isImplementsOf(type, Comparable.class)) {
ret = ((Comparable) f.get(a)).compareTo((Comparable) f
.get(b));
} else {
ret = String.valueOf(f.get(a)).compareTo(
String.valueOf(f.get(b)));
}
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
if (sort != null && sort.toLowerCase().equals(DESC)) {
return -ret;
} else {
return ret;
}
}
});
return list;
}
/**
* 對list中的元素按fields和sorts進行排序,
* fields[i]指定排序字段,sorts[i]指定排序方式.如果sorts[i]為空則默認按升序排列.
*
* @param list
* @param fields
* @param sorts
* @return
*/
@SuppressWarnings("unchecked")
public static List<?> sort(List<?> list, String[] fields, String[] sorts) {
if (fields != null && fields.length > 0) {
for (int i = fields.length - 1; i >= 0; i--) {
final String field = fields[i];
String tmpSort = ASC;
if (sorts != null && sorts.length > i && sorts[i] != null) {
tmpSort = sorts[i];
}
final String sort = tmpSort;
Collections.sort(list, new Comparator() {
public int compare(Object a, Object b) {
int ret = 0;
try {
Field f = a.getClass().getDeclaredField(field);
f.setAccessible(true);
Class<?> type = f.getType();
if (type == int.class) {
ret = ((Integer) f.getInt(a))
.compareTo((Integer) f.getInt(b));
} else if (type == double.class) {
ret = ((Double) f.getDouble(a))
.compareTo((Double) f.getDouble(b));
} else if (type == long.class) {
ret = ((Long) f.getLong(a)).compareTo((Long) f
.getLong(b));
} else if (type == float.class) {
ret = ((Float) f.getFloat(a))
.compareTo((Float) f.getFloat(b));
} else if (type == Date.class) {
ret = ((Date) f.get(a)).compareTo((Date) f
.get(b));
} else if (isImplementsOf(type, Comparable.class)) {
ret = ((Comparable) f.get(a))
.compareTo((Comparable) f.get(b));
} else {
ret = String.valueOf(f.get(a)).compareTo(
String.valueOf(f.get(b)));
}
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
if (sort != null && sort.toLowerCase().equals(DESC)) {
return -ret;
} else {
return ret;
}
}
});
}
}
return list;
}
/**
* 默認按正序排列
*
* @param list
* @param method
* @return
*/
public static List<?> sortByMethod(List<?> list, final String method) {
return sortByMethod(list, method, null);
}
@SuppressWarnings("unchecked")
public static List<?> sortByMethod(List<?> list, final String method,
final String sort) {
Collections.sort(list, new Comparator() {
public int compare(Object a, Object b) {
int ret = 0;
try {
Method m = a.getClass().getMethod(method, null);
m.setAccessible(true);
Class<?> type = m.getReturnType();
if (type == int.class) {
ret = ((Integer) m.invoke(a, null))
.compareTo((Integer) m.invoke(b, null));
} else if (type == double.class) {
ret = ((Double) m.invoke(a, null)).compareTo((Double) m
.invoke(b, null));
} else if (type == long.class) {
ret = ((Long) m.invoke(a, null)).compareTo((Long) m
.invoke(b, null));
} else if (type == float.class) {
ret = ((Float) m.invoke(a, null)).compareTo((Float) m
.invoke(b, null));
} else if (type == Date.class) {
ret = ((Date) m.invoke(a, null)).compareTo((Date) m
.invoke(b, null));
} else if (isImplementsOf(type, Comparable.class)) {
ret = ((Comparable) m.invoke(a, null))
.compareTo((Comparable) m.invoke(b, null));
} else {
ret = String.valueOf(m.invoke(a, null)).compareTo(
String.valueOf(m.invoke(b, null)));
}
if (isImplementsOf(type, Comparable.class)) {
ret = ((Comparable) m.invoke(a, null))
.compareTo((Comparable) m.invoke(b, null));
} else {
ret = String.valueOf(m.invoke(a, null)).compareTo(
String.valueOf(m.invoke(b, null)));
}
} catch (NoSuchMethodException ne) {
System.out.println(ne);
} catch (IllegalAccessException ie) {
System.out.println(ie);
} catch (InvocationTargetException it) {
System.out.println(it);
}
if (sort != null && sort.toLowerCase().equals(DESC)) {
return -ret;
} else {
return ret;
}
}
});
return list;
}
@SuppressWarnings("unchecked")
public static List<?> sortByMethod(List<?> list, final String methods[],
final String sorts[]) {
if (methods != null && methods.length > 0) {
for (int i = methods.length - 1; i >= 0; i--) {
final String method = methods[i];
String tmpSort = ASC;
if (sorts != null && sorts.length > i && sorts[i] != null) {
tmpSort = sorts[i];
}
final String sort = tmpSort;
Collections.sort(list, new Comparator() {
public int compare(Object a, Object b) {
int ret = 0;
try {
Method m = a.getClass().getMethod(method, null);
m.setAccessible(true);
Class<?> type = m.getReturnType();
if (type == int.class) {
ret = ((Integer) m.invoke(a, null))
.compareTo((Integer) m.invoke(b, null));
} else if (type == double.class) {
ret = ((Double) m.invoke(a, null))
.compareTo((Double) m.invoke(b, null));
} else if (type == long.class) {
ret = ((Long) m.invoke(a, null))
.compareTo((Long) m.invoke(b, null));
} else if (type == float.class) {
ret = ((Float) m.invoke(a, null))
.compareTo((Float) m.invoke(b, null));
} else if (type == Date.class) {
ret = ((Date) m.invoke(a, null))
.compareTo((Date) m.invoke(b, null));
} else if (isImplementsOf(type, Comparable.class)) {
ret = ((Comparable) m.invoke(a, null))
.compareTo((Comparable) m.invoke(b,
null));
} else {
ret = String.valueOf(m.invoke(a, null))
.compareTo(
String.valueOf(m
.invoke(b, null)));
}
} catch (NoSuchMethodException ne) {
System.out.println(ne);
} catch (IllegalAccessException ie) {
System.out.println(ie);
} catch (InvocationTargetException it) {
System.out.println(it);
}
if (sort != null && sort.toLowerCase().equals(DESC)) {
return -ret;
} else {
return ret;
}
}
});
}
}
return list;
}
/**
* 判斷對象實現的所有接口中是否包含szInterface
*
* @param clazz
* @param szInterface
* @return
*/
public static boolean isImplementsOf(Class<?> clazz, Class<?> szInterface) {
boolean flag = false;
Class<?>[] face = clazz.getInterfaces();
for (Class<?> c : face) {
if (c == szInterface) {
flag = true;
} else {
flag = isImplementsOf(c, szInterface);
}
}
if (!flag && null != clazz.getSuperclass()) {
return isImplementsOf(clazz.getSuperclass(), szInterface);
}
return flag;
}
public static void main(String[] args) throws Exception {
List<Student> list = new ArrayList<Student>();
list.add(new Student(3, "b", 1, new Date(11110000)));
list.add(new Student(1, "c", 3, new Date(44440000)));
list.add(new Student(2, "a", 2, new Date(22210000)));
list.add(new Student(4, "a", 11, new Date(33330000)));
System.out.println("-------原來序列-------------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// 按age正序排序,注意結果排完後是1,2,3,11. 不是1,11,2,3(如果是String類型正序排序是這樣)
SortListUtil.sort(list, "age", null);
System.out.println("---------測試Integer和正序,按age正序排序-----------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// 按id倒序
SortListUtil.sort(list, "id", SortListUtil.DESC);
System.out.println("--------測試int和倒序,按id倒序------------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// 先按name正序排序,再按id正序排序
SortListUtil.sort(list, new String[] { "name", "id" }, new String[] {});
System.out
.println("---------測試多個排序字段,先按name正序,name相同時再按id正序-----------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// 先按name正序排序,再按id倒序排序
SortListUtil.sort(list, new String[] { "name", "id" }, new String[] {
SortListUtil.ASC, SortListUtil.DESC });
System.out
.println("---------測試多個排序字段,先按name正序,name相同時再按id倒序-----------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// 按birthday排序
SortListUtil.sort(list, "birthday");
System.out
.println("---------測試實現了Comparable接口的對象排序,按birthday正序-----------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
// sortByMethod
SortListUtil.sortByMethod(list, "getId", null);
System.out
.println("---------測試sortByMethod,按getId方法正序-----------------");
for (Student stu : list) {
System.out.println(stu.toString());
}
}
}
測試執行效果: