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