Java 中比较时间

17 Mar 2025 | 4 分钟阅读

大多数时候我们需要比较两个日期和日期时间对象。当我们需要从数据库中获取特定日期和时间的数据，或者根据日期和时间过滤返回的数据时，就需要进行日期比较。

为了比较时间，我们使用 LocalTime 类的 compareTo() 方法。该类的 compareTo() 方法用于比较两个 LocalTime 对象。第一个 LocalTime 对象是我们想要比较的对象，第二个对象是我们作为参数传递给 compareTo() 方法的对象，并且我们想要与此 LocalTime 对象进行比较。

语法

LocalTime 类的 compareTo() 方法如下：

参数

它只接受一个参数，即要比较的 LocalTime 对象，并且该对象不应为 null。

返回值

compareTo() 方法根据对象的比较返回三个值：

当此 LocalTime 对象大于指定的 LocalTime 对象时，它返回一个正值。
当此 LocalTime 对象小于指定的 LocalTime 对象时，它返回一个负值。
当此 LocalTime 对象等于指定的 LocalTime 对象时，它返回零。

让我们通过一些例子来理解 compareTo() 方法是如何用于比较两个 LocalTime 对象的。

CompareToExample1.java

// import required classes and packages
import java.time.*;
import java.util.Scanner;
// create CompareToExample1 class to understand the working of CompareTo() method
public class CompareToExample1 {
	// main() method start
	public static void main(String[] args)
	{
		// declare variable for initialize LocalTime
		int hour1, hour2, min1, min2, sec1, sec2;
		LocalTime time1, time2;
		// create Scanner class object to take input from the user for initializing LocalTime
		Scanner sc = new Scanner(System.in);
		// get input from used for initializing time1
		System.out.println("Enter time for initializing the first LocaleTime object:");
		System.out.println("Enter hours:");
		hour1 = sc.nextInt();
		System.out.println("Enter minutes:");
		min1 = sc.nextInt();
		System.out.println("Enter seconds:");
		sec1 = sc.nextInt();
		// initialize LocalTime object for time1
		time1 = LocalTime.of(hour1, min1, sec1);
		// get input from used for initializing time2
		System.out.println("Enter time for initializing the second LocaleTime object:");
		System.out.println("Enter hours:");
		hour2 = sc.nextInt();
		System.out.println("Enter minutes:");
		min2 = sc.nextInt();
		System.out.println("Enter seconds:");
		sec2 = sc.nextInt();
		// close scanner class object
		sc.close();
		// initialize LocalTime object for time2
		time2 = LocalTime.of(hour2, min2, sec2);
		// use compareTo() method to compare time1 and time2 objects
		int returnVal = time1.compareTo(time2);
		// print value return by 
		System.out.println("Value returned by comparTo() method:" + returnVal);
		// check whether the time1 object is greater, smaller or equal to time2
		if (returnVal > 0) {
			System.out.println("time1 is greater than time2.");
		}else if (returnVal == 0) {
			System.out.println("time1 is equal to time2.");
		}else {
			System.out.println("time1 is smaller than time2.");
		}
	}
}

输出

让我们再举一个例子来理解 compareTo() 方法的概念。在这个例子中，我们将使用 compareTo() 方法比较两个日期时间对象。

CompareToExample2.java

//import required classes and packages
package javaTpoint.JavaExample;

import java.time.*;
import java.util.Scanner;

//create CompareToExample1 class to understand the working of CompareTo() method
public class CompareToExample2 {
	
	// main() method start
	public static void main(String[] args)
	{
		// declare variable for initialize LocaleDateTime
		int hour1, hour2, min1, min2, sec1, sec2, yr1, yr2, month1, month2, day1, day2;
		LocalDateTime date1, date2;
		
		// create Scanner class object to take input from the user for initializing LocaleDateTime
		Scanner sc = new Scanner(System.in);
		
		// get input from used for initializing date1
		System.out.println("Enter Datetime for initializing the first LocaleDateTime object:");
		System.out.println("Enter year:");
		yr1 = sc.nextInt();
		System.out.println("Enter month:");
		month1 = sc.nextInt();
		System.out.println("Enter day:");
		day1 = sc.nextInt();
		System.out.println("Enter hours:");
		hour1 = sc.nextInt();
		System.out.println("Enter minutes:");
		min1 = sc.nextInt();
		System.out.println("Enter seconds:");
		sec1 = sc.nextInt();
		
		// initialize LocaleDateTime object for date1
		date1 = LocalDateTime.of(yr1, month1, day1, hour1, min1, sec1);
		System.out.println("Date1: " + date1);
		
		// get input from used for initializing time2
		System.out.println("Enter Datetime for initializing the second LocaleDateTime object:");
		System.out.println("Enter year:");
		yr2 = sc.nextInt();
		System.out.println("Enter month:");
		month2 = sc.nextInt();
		System.out.println("Enter day:");
		day2 = sc.nextInt();
		System.out.println("Enter hours:");
		hour2 = sc.nextInt();
		System.out.println("Enter minutes:");
		min2 = sc.nextInt();
		System.out.println("Enter seconds:");
		sec2 = sc.nextInt();
		
		// close scanner class object
		sc.close();
		
		// initialize LocalTime object for date2
		date2 = LocalDateTime.of(yr2, month2, day2, hour2, min2, sec2);
		System.out.println("Date2: " + date2);
		
		// use compareTo() method to compare date1 and date2 objects
		int returnVal = date1.compareTo(date2);

		// print value return by 
		System.out.println("Value returned by comparTo() method:" + returnVal);
		
		// check whether the date1 object is greater, smaller or equal to date2
		if (returnVal > 0) {
			System.out.println("date1 is greater than date2.");
		}else if (returnVal == 0) {
			System.out.println("date1 is equal to date2.");
		}else {
			System.out.println("date1 is smaller than date2.");
		}
	}
}

输出

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