Java ConcurrentHashMap isEmpty()用法及代码示例

java.util.concurrent.ConcurrentHashMap的isEmpty()方法是Java中的内置函数，该函数检查此映射是否包含任何键-值映射并返回布尔值。

用法:

public boolean isEmpty()

返回值：该函数返回一个布尔值。如果ConcurrentHashMap为空，则返回true，否则返回false。

以下示例程序旨在说明isEmpty()方法的使用：

示例1:在此程序中，ConcurrentHashMap是非空的。

// Java Program Demonstrate isEmpty() 
// method of ConcurrentHashMap */ 
  
import java.util.concurrent.*; 
  
class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        ConcurrentHashMap<Integer, String> 
            chm = new ConcurrentHashMap<Integer, String>(); 
  
        chm.put(100, "Geeks"); 
        chm.put(101, "for"); 
        chm.put(102, "Geeks"); 
  
        // Checking for the emptiness of Map 
        if (chm.isEmpty()) { 
            System.out.println("The ConcurrentHashMap"
                               + " is empty."); 
        } 
        else { 
            // Displaying the ConcurrentHashMap 
            System.out.println("The Mappings are: "
                               + chm); 
        } 
    } 
}

输出：

The Mappings are: {100=Geeks, 101=for, 102=Geeks}

示例2:在此程序中，ConcurrentHashMap是非空的。

// Java Program Demonstrate isEmpty() 
// method of ConcurrentHashMap */ 
  
import java.util.concurrent.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        ConcurrentHashMap chm = new ConcurrentHashMap(); 
  
        // Checking for the emptiness of Map 
        if (chm.isEmpty()) { 
            System.out.println("The ConcurrentHashMap"
                               + " is empty."); 
        } 
        else { 
            // Displaying the ConcurrentHashMap 
            System.out.println("The Mappings are: "
                               + chm); 
        } 
    } 
}

输出：

The ConcurrentHashMap is empty.

参考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html#isEmpty()

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注：本文由纯净天空筛选整理自RICHIK BHATTACHARJEE大神的英文原创作品 ConcurrentHashMap isEmpty() Method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。