Java 8 Clock equals()用法及代碼示例

Java Clock類是Java的Date Time API(java.time.Clock)的一部分。 Java日期時間API是從Java版本8添加的。

java.time.Clock類的equals()方法檢查兩個Clock對象是否相等。如果時鍾相等，則返回true，否則返回false。時鍾類的equals方法重寫此Object.equals(java.lang.Object)方法以根據時鍾對象狀態進行比較。如果未重寫，則此equal()方法采用java.lang.Object.equals()的描述

用法:

public boolean equals(Object obj)

參數：此方法采用強製性參數obj，該參數是傳遞的時鍾對象，用於與現有時鍾對象進行比較。

返回值：如果兩個時鍾對象相等，則此方法返回true。否則，它返回false。

例：

Input: 
Clock object of ZoneId "UTC"
Clock object of ZoneId "Asia/calcutta"

Output:
false

Explanation:
Both objects represent Clock object of the different zone.
Hence applying equals on them returns false.

下麵的程序演示了java.time.Clock類的equals()方法：

示例1:比較兩個相似的類對象時。

// Java program to demonstrate equals() 
// method of Clock class 
  
import java.time.Clock; 
import java.time.ZoneId; 
  
// create class 
public class EqualsMethodDemo { 
  
    // Main method 
    public static void main(String[] args) 
    { 
  
        // create clock object which represents 
        // UTC Zone time using system() 
        Clock clock1 = Clock.system(ZoneId.of("Etc/UTC")); 
  
        // Print Clock1 details 
        System.out.println(clock1.toString()); 
  
        // Create another class Object using 
        // clock class systemDefaultZone method 
        Clock clock2 = Clock.systemDefaultZone(); 
  
        // Print Clock2 details 
        System.out.println(clock2.toString()); 
  
        // check whether both clock obejcts are equal or not 
        boolean equalResponse = clock1.equals(clock2); 
  
        // print result 
        System.out.println("Both clocks are equal:"
                           + equalResponse); 
    } 
}

輸出：

SystemClock[Etc/UTC]
SystemClock[Etc/UTC]
Both clocks are equal:true

示例2:比較兩個不同的類對象時。

// Java program to demonstrate equals() 
// method of Clock class 
  
import java.time.Clock; 
import java.time.ZoneId; 
  
// create class 
public class EqualsMethodDemo { 
  
    // Main method 
    public static void main(String[] args) 
    { 
  
        // Create a class Object using clock 
        // class systemDefaultZone method 
        Clock clock1 = Clock.systemDefaultZone(); 
  
        // Print Clock1 Zone details 
        System.out.println("clock1 Time Zone = "
                           + clock1.getZone()); 
  
        // Create another class Object using 
        // clock class systemUTC method 
        Clock clock2 = Clock.systemUTC(); 
  
        // Print Clock2 Zone details 
        System.out.println("clock2 Time Zone = "
                           + clock2.getZone()); 
  
        // check whether both clock obejcts are equal or not 
        boolean equalResponse = clock1.equals(clock2); 
  
        // print result 
        System.out.println("Both clocks are equal:"
                           + equalResponse); 
    } 
}

輸出：

clock1 Time Zone = Etc/UTC
clock2 Time Zone = Z
Both clocks are equal:false

參考： https://docs.oracle.com/javase/8/docs/api/java/time/Clock.html#equals-java.lang.Object-

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