Java Instant compareTo()方法及示例

Instant类的 compareTo(Instant otherInstant) 方法用于比较本实例和作为参数传递的实例，以检查两个实例是否相等。两个实例之间的比较是基于两个实例的时间线位置。这个方法返回的值是按以下方式确定的。

语法

public int compareTo(Instant otherInstant)

参数： 该方法接受一个强制性的参数 otherInstant ，它是被比较的另一个瞬间，并且它不应该是空的。

返回值： 该方法返回一个整数值，如下所示。

异常： 如果作为参数传递的其他Instant是空的，这个方法会抛出 NullPointerException 。

下面的程序说明了Instant.compareTo()方法。

程序1： 当这个实例大于

// Java program to demonstrate// Instant.compareTo() method  import java.time.*;  public class GFG {    public static void main(String[] args)    {          // create two instance objects        Instant instant1            = Instant.parse("2018-10-20T16:55:30.00Z");          Instant instant2            = Instant.parse("2017-10-20T16:55:30.00Z");          // print Instant Values        System.out.println("Instant1: "                           + instant1);        System.out.println("Instant2: "                           + instant2);          // compare both instant        int value = instant1.compareTo(instant2);          if (value > 0)            System.out.println("Instant1 is greater");        else if (value == 0)            System.out.println("Instant1 is equal to Instant2");        else            System.out.println("Instant2 is greater");    }}

输出:

Instant1: 2018-10-20T16:55:30ZInstant2: 2017-10-20T16:55:30ZInstant1 is greater

程序2： 当作为参数传递的另一个Instant更大时

// Java program to demonstrate// Instant.compareTo() method  import java.time.*;  public class GFG {    public static void main(String[] args)    {          // create two instance objects        Instant instant1            = Instant.parse("2017-10-20T16:55:30.00Z");          Instant instant2            = Instant.parse("2018-10-20T16:55:30.00Z");          // print Instant Values        System.out.println("Instant1: "                           + instant1);        System.out.println("Instant2: "                           + instant2);          // compare both instant        int value = instant1.compareTo(instant2);          if (value > 0)            System.out.println("Instant1 is greater");        else if (value == 0)            System.out.println("Instant1 is equal to Instant2");        else            System.out.println("Instant2 is greater");    }}

输出:

Instant1: 2017-10-20T16:55:30ZInstant2: 2018-10-20T16:55:30ZInstant2 is greater

方案1： 当两个实例相等时

// Java program to demonstrate// Instant.compareTo() method  import java.time.*;  public class GFG {    public static void main(String[] args)    {          // create two instance objects        Instant instant1            = Instant.parse("2018-10-20T16:55:30.00Z");          Instant instant2            = Instant.parse("2018-10-20T16:55:30.00Z");          // print Instant Values        System.out.println("Instant1: "                           + instant1);        System.out.println("Instant2: "                           + instant2);          // compare both instant        int value = instant1.compareTo(instant2);          if (value > 0)            System.out.println("Instant1 is greater");        else if (value == 0)            System.out.println("Instant1 is equal to Instant2");        else            System.out.println("Instant2 is greater");    }}

输出:

Instant1: 2018-10-20T16:55:30ZInstant2: 2018-10-20T16:55:30ZInstant1 is equal to Instant2

程序4： 显示NullPointer异常

// Java program to demonstrate// Instant.compareTo() method  import java.time.*;  public class GFG {    public static void main(String[] args)    {          // create two instance objects        Instant instant1            = Instant.parse("2018-10-20T16:55:30.00Z");          Instant instant2 = null;          try {              // compare both instant            int value = instant1.compareTo(instant2);        }        catch (NullPointerException e) {            System.out.println("Exception: " + e);        }    }}

输出:

Exception: java.lang.NullPointerException

**参考资料: ** https://docs.oracle.com/javase/10/docs/api/java/time/Instant.html#compareTo(java.time.instant)