Java8中List排序让代码更加优雅的排序方法

在做wab项目中不免会做后台管理，后台最常见的就是表格了，这时候按照一般规则都会按照某个属性进行排序，像这种List<实体>类型的甚为常见。下面给大家分享三种按照属性中的某一个字段排序的例子，有用到的朋友自取~~

1、stream写法

//按提交时间降序--stream写法
List companyList =this.mapper.selectCompany(param);//根据参数查询符合的实体列表
companyList = companyList.stream().sorted(Comparator.comparing(Company::getCreateTime).reversed()).collect(Collectors.toList());//根据创建时间倒排


Stream API是Java8中处理集合的关键组件，提供了各种丰富的函数式操作。

2、Collections写法

//按提交时间降序 --Lamdba表达式
Collections.sort(companyList, (a, b) -> b.getCreateTime().compareTo(a.getCreateTime()));


3、借助工具类—常规写法

//按提交时间降序--工具类写法
SortListUtil.sort(companyList,"createTime","desc");


工具类：

package com.jdy.core.util;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;
import org.springframework.util.CollectionUtils;
/**
* 通用工具类之按对象中某属性排序 *
*/
public class SortListUtil {
public static final String DESC = "desc";
public static final String ASC = "asc";
/**
* 对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);
}
/**
* 对list中的元素进行排序.
*
* @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) {
if (CollectionUtils.isEmpty(list)) {
return list;
}
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;
}
/**
* 对list中的元素按fields和sorts进行排序,
* fields[i]指定排序字段,sorts[i]指定排序方式.如果sorts[i]为空则默认按升序排列.
*
* @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;
}
/**
* 默认按正序排列
*
* @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;
}
/**
* 判断对象实现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;
}


}

参考链接：
Java8体验（二）Stream语法详解
java8 Stream