总结Java集合List按日期升序或降序常见的四种方法如下

四种方法快速预览

Method 1、不管是Date、String、Long类型的日期都可以排序，无需转换

orders.sort((t1, t2) -> t2.getPayTime().compareTo(t1.getPayTime()));

Method 2、利用stream，需要把字符串日期转换为时间戳

orders = orders.stream().sorted((t1,t2) -> 
		 			Long.compare(convertTimeToLong(t2.getPayTime()), 
		 			convertTimeToLong(t1.getPayTime()))).
				 collect(Collectors.toList());

Method 3、利用Comparator接口实现，java8的写法

Collections.sort(orders, Comparator.comparing(Order::getPayTime, (t1, t2) -> t2.compareTo(t1)));

Method 4、利用Comparator接口实现，java8之前通常这样写

Collections.sort(orders,new Comparator<Order>(){
		@Override
		public int compare(Order o1, Order o2) {
			return o2.getPayTime().compareTo(o1.getPayTime());
		}
});

准备的类

import lombok.AllArgsConstructor;
import lombok.Data;

@AllArgsConstructor
@Data
class Order {
	/**
	 * 订单号
	 */
    private String orderNum;
    
    /**
	 * 付款时间
	 */
    private String payTime;
    
    /**
	 * 支付金额
	 */
    private Integer actualAmount;
}

方法一

import java.util.ArrayList;
import java.util.List;

public class TestTimeSort {
	public static void main(String[] args) {
		Order order1 = new Order("1101", "2019-11-03 00:30:31", 100);
		Order order2 = new Order("1102", "2019-11-03 00:30:32", 200);
		Order order3 = new Order("1103", "2019-11-03 00:30:33", 300);
		Order order4 = new Order("1104", "2019-11-03 00:30:34", 400);
		Order order5 = new Order("1105", "2019-11-03 00:30:35", 500);
		List<Order> orders = new ArrayList<>();
		orders.add(order2);
		orders.add(order1);
		orders.add(order4);
		orders.add(order3);
		orders.add(order5);
		System.out.println("------------排序前-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
        //不管是Date、String、Long类型的日期都可以排序，无需转换
		orders.sort((t1, t2) -> t2.getPayTime().compareTo(t1.getPayTime()));
		System.out.println("------------倒序后-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
	}
}

方法二

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class TestTimeSort {
	public static void main(String[] args) {
		Order order1 = new Order("1101", "2019-11-03 00:30:31", 100);
		Order order2 = new Order("1102", "2019-11-03 00:30:32", 200);
		Order order3 = new Order("1103", "2019-11-03 00:30:33", 300);
		Order order4 = new Order("1104", "2019-11-03 00:30:34", 400);
		Order order5 = new Order("1105", "2019-11-03 00:30:35", 500);
		List<Order> orders = new ArrayList<>();
		orders.add(order2);
		orders.add(order1);
		orders.add(order4);
		orders.add(order3);
		orders.add(order5);
		System.out.println("------------排序前-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
        //利用stream，需要把字符串日期转换为时间戳
		 orders = orders.stream().sorted((t1,t2) -> 
		 			Long.compare(convertTimeToLong(t2.getPayTime()), convertTimeToLong(t1.getPayTime()))).
				 collect(Collectors.toList());
		System.out.println("------------倒序后-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
	}
    
    /**
     * 将字符串转日期成Long类型的时间戳，格式为：yyyy-MM-dd HH:mm:ss
     */
    public static Long convertTimeToLong(String time) { 
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime parse = LocalDateTime.parse(time, formatter);
        return LocalDateTime.from(parse).atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
    }  
}

方法三

import java.util.ArrayList;
import java.util.List;
import java.util.Collections;
import java.util.Comparator;

public class TestTimeSort {
	public static void main(String[] args) {
		Order order1 = new Order("1101", "2019-11-03 00:30:31", 100);
		Order order2 = new Order("1102", "2019-11-03 00:30:32", 200);
		Order order3 = new Order("1103", "2019-11-03 00:30:33", 300);
		Order order4 = new Order("1104", "2019-11-03 00:30:34", 400);
		Order order5 = new Order("1105", "2019-11-03 00:30:35", 500);
		List<Order> orders = new ArrayList<>();
		orders.add(order2);
		orders.add(order1);
		orders.add(order4);
		orders.add(order3);
		orders.add(order5);
		System.out.println("------------排序前-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
        //利用Comparator接口实现，java8的写法
		Collections.sort(orders, Comparator.comparing(Order::getPayTime, (t1, t2) -> t2.compareTo(t1)));
		System.out.println("------------倒序后-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
	}
}

方法四

import java.util.ArrayList;
import java.util.List;
import java.util.Collections;
import java.util.Comparator;

public class TestTimeSort {
	public static void main(String[] args) {
		Order order1 = new Order("1101", "2019-11-03 00:30:31", 100);
		Order order2 = new Order("1102", "2019-11-03 00:30:32", 200);
		Order order3 = new Order("1103", "2019-11-03 00:30:33", 300);
		Order order4 = new Order("1104", "2019-11-03 00:30:34", 400);
		Order order5 = new Order("1105", "2019-11-03 00:30:35", 500);
		List<Order> orders = new ArrayList<>();
		orders.add(order2);
		orders.add(order1);
		orders.add(order4);
		orders.add(order3);
		orders.add(order5);
		System.out.println("------------排序前-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
        //利用Comparator接口实现，java8之前通常这样写
		Collections.sort(orders,new Comparator<Order>(){
			@Override
			public int compare(Order o1, Order o2) {
				return o2.getPayTime().compareTo(o1.getPayTime());
			}
		});
		System.out.println("------------倒序后-----------------");
		for (Order order : orders) {
			System.out.println("orderNum=" + order.getOrderNum() + ",payTime=" + order.getPayTime());
		}
	}
}

四种方法最后输出如下

------------排序前-----------------
orderNum=1102,payTime=2019-11-03 00:30:32
orderNum=1101,payTime=2019-11-03 00:30:31
orderNum=1104,payTime=2019-11-03 00:30:34
orderNum=1103,payTime=2019-11-03 00:30:33
orderNum=1105,payTime=2019-11-03 00:30:35
------------倒序后-----------------
orderNum=1105,payTime=2019-11-03 00:30:35
orderNum=1104,payTime=2019-11-03 00:30:34
orderNum=1103,payTime=2019-11-03 00:30:33
orderNum=1102,payTime=2019-11-03 00:30:32
orderNum=1101,payTime=2019-11-03 00:30:31
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