Java CopyOnWriteArraySet isEmpty()用法及代碼示例

CopyOnWriteArraySet的isEmpty(E e)方法檢查Set是否為空。如果Set為空，則返回true，否則返回false。

用法:

public boolean isEmpty()

返回值：如果Set為空，則該函數返回true，否則返回false。

以下示例程序旨在說明上述函數：

示例1:

// Java Program to illustrate the 
// isEmpty() method in Java 
  
import java.util.concurrent.CopyOnWriteArraySet; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create object of CopyOnWriteArraySet 
        CopyOnWriteArraySet<Integer> ArrSet 
            = new CopyOnWriteArraySet<Integer>(); 
  
        // Add elements 
        ArrSet.add(32); 
        ArrSet.add(67); 
        ArrSet.add(98); 
        ArrSet.add(100); 
  
        // print CopyOnWriteArraySet 
        System.out.println("CopyOnWriteArraySet: " + ArrSet); 
  
        // check using function 
        if (ArrSet.isEmpty()) 
            System.out.println("\nSet is empty"); 
        else
            System.out.println("\nSet is not empty"); 
    } 
}

輸出：

CopyOnWriteArraySet: [32, 67, 98, 100]

Set is not empty

示例2:

// Java Program to illustrate the 
// isEmpty() method in Java 
import java.util.concurrent.CopyOnWriteArraySet; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create object of CopyOnWriteArraySet 
        CopyOnWriteArraySet<String> ArrSet 
            = new CopyOnWriteArraySet<String>(); 
  
        // print CopyOnWriteArraySet 
        System.out.println("CopyOnWriteArraySet: "
                           + ArrSet); 
  
        // check using function 
        if (ArrSet.isEmpty()) 
            System.out.println("\nSet is empty"); 
        else
            System.out.println("\nSet is not empty"); 
    } 
}

輸出：

CopyOnWriteArraySet: []

Set is empty

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArraySet.html#isEmpty–

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