java.time.LocalDateTime比较大小方法

 1.now() : 获取当前时间

    //源码
    public static LocalDateTime now() {
        return now(Clock.systemDefaultZone());
    }

    //获取当前时间  年月日 时分秒
    LocalDateTime localDateTime = LocalDateTime.now();
    System.out.println("localDateTime = " + localDateTime);

输出结果:         localDateTime = 2023-03-08T21:28:17.617

2.format() : 格式化LocalDateTime

    //源码    
    @Override  // override for Javadoc and performance    
    public String format(DateTimeFormatter formatter) {
        Objects.requireNonNull(formatter, "formatter");
        return formatter.format(this);
    }

    LocalDateTime localDateTime = LocalDateTime.now();
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    String format = localDateTime.format(dateTimeFormatter);
    System.out.println(format);

输出结果:        2023-03-03 15:18:58

 3. toLocalDate() : 日期时间转化成日期

    //源码
    @Override        
    public LocalDate toLocalDate() {
        return date;
    }

    LocalDateTime localDateTime = LocalDateTime.now();
    LocalDate localDate = localDateTime.toLocalDate();
    System.out.println(localDate);

输出结果:         2023-03-08

4. isAfter() : 判断时间大小关系

    // 源码
    @Override  // override for Javadoc and performance
    public boolean isAfter(ChronoLocalDateTime other) {
        if (other instanceof LocalDateTime) {
            return compareTo0((LocalDateTime) other) > 0;
        }
        return ChronoLocalDateTime.super.isAfter(other);
    }

    System.out.println("nowLocalDateTime = " + nowLocalDateTime);
    System.out.println("oldLocalDateTime = " + oldLocalDateTime);
    // 判断调用者是否在传入参数(时间)之后
    boolean after = nowLocalDateTime.isAfter(oldLocalDateTime);
    System.out.println(after);

输出结果:   

                nowLocalDateTime = 2023-03-03T22:37:32.160
                oldLocalDateTime = 2023-03-03T10:33:44.160

                true

5. isBefore() : 判断时间大小关系

    // 源码
    @Override  // override for Javadoc and performance
    public boolean isBefore(ChronoLocalDateTime other) {
        if (other instanceof LocalDateTime) {
            return compareTo0((LocalDateTime) other) < 0;
        }
        return ChronoLocalDateTime.super.isBefore(other);
    }

    System.out.println("nowLocalDateTime = " + nowLocalDateTime);
    System.out.println("oldLocalDateTime = " + oldLocalDateTime);
    // 判断调用者是否在传入参数(时间)之前
    boolean before = nowLocalDateTime.isBefore(oldLocalDateTime);
    System.out.println(before);

输出结果:   

                nowLocalDateTime = 2023-03-03T22:43:03.391
                oldLocalDateTime = 2023-03-03T10:33:44.160
                false

6.compareTo() : 判断时间大小关系

    // 源码
    @Override  // override for Javadoc and performance
    public int compareTo(ChronoLocalDateTime other) {
        if (other instanceof LocalDateTime) {
            return compareTo0((LocalDateTime) other);
        }
        return ChronoLocalDateTime.super.compareTo(other);
    }

    System.out.println("nowLocalDateTime = " + nowLocalDateTime);
    System.out.println("oldLocalDateTime = " + oldLocalDateTime);
    // 当日期不同时,返回日期差
    // 当日期相同时,返回1或-1
    int nowToOld = nowLocalDateTime.compareTo(oldLocalDateTime);
    int oldToNow = oldLocalDateTime.compareTo(nowLocalDateTime);
    
    System.out.println(nowToOld);
    System.out.println(oldToNow);

输出结果:   

                // 当两个时间日期不同时,返回日期差值

                // 返回正数 即 调用方法的时间晚于传参时间 , 反之则早于传参时间 

                nowLocalDateTime = 2023-02-13T22:43:03.391
                oldLocalDateTime = 2023-02-03T10:33:44.160
                10

                -10

                

                // 当两个时间日期相同时,返回1或-1

                // 返回1 即 调用方法的时间晚于传参时间 , 反之则早于传参时间 

                nowLocalDateTime = 2023-03-03T22:43:03.391
                oldLocalDateTime = 2023-03-03T10:33:44.160
                1

                -1