Java Dictionary isEmpty()用法及代码示例

字典类的isEmpty()方法检查此字典是否具有任何键-值映射。仅当此词典中没有条目时，该函数才返回TRUE。

用法:

public abstract boolean isEmpty()

返回值：如果字典为空，则该函数返回TRUE，否则返回FALSE。

异常：该函数不会引发异常。

以下示例程序旨在说明Dictionary.isEmpty()方法的使用：

示例1:

// Java Program to illustrate 
// Dictionary.isEmpty() method 
  
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // Create a new hashtable 
        Dictionary<Integer, String> 
            d = new Hashtable<Integer, String>(); 
  
        // Insert elements in the hashtable 
        d.put(1, "Geeks"); 
        d.put(2, "for"); 
        d.put(3, "Geeks"); 
  
        // Print the Dictionary 
        System.out.println("\nDictionary: " + d); 
  
        // check if this dictionary is empty 
        // using isEmpty() method 
        if (d.isEmpty()) { 
            System.out.println("Dictionary "
                               + "is empty"); 
        } 
        else
            System.out.println("Dictionary "
                               + "is not empty"); 
    } 
}

输出：

Dictionary: {3=Geeks, 2=for, 1=Geeks}
Dictionary is not empty

示例2:

// Java Program to illustrate 
// Dictionary.isEmpty() method 
  
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // Create a new hashtable 
        Dictionary<String, String> 
            d = new Hashtable<String, String>(); 
  
        // Print the Dictionary 
        System.out.println("\nDictionary: " + d); 
  
        // check if this dictionary is empty 
        // using isEmpty() method 
        if (d.isEmpty()) { 
            System.out.println("Dictionary "
                               + "is empty"); 
        } 
        else
            System.out.println("Dictionary "
                               + "is not empty"); 
  
        // Insert elements in the hashtable 
        d.put("a", "GFG"); 
        d.put("b", "gfg"); 
  
        // Print the Dictionary 
        System.out.println("\nDictionary: " + d); 
  
        // check if this dictionary is empty 
        // using isEmpty() method 
        if (d.isEmpty()) { 
            System.out.println("Dictionary "
                               + "is empty"); 
        } 
        else
            System.out.println("Dictionary "
                               + "is not empty"); 
  
        // Remove elements in the hashtable 
        d.remove("a"); 
        d.remove("b"); 
  
        // Print the Dictionary 
        System.out.println("\nDictionary: " + d); 
  
        // check if this dictionary is empty 
        // using isEmpty() method 
        if (d.isEmpty()) { 
            System.out.println("Dictionary "
                               + "is empty"); 
        } 
        else
            System.out.println("Dictionary "
                               + "is not empty"); 
    } 
}

输出：

Dictionary: {}
Dictionary is empty

Dictionary: {b=gfg, a=GFG}
Dictionary is not empty

Dictionary: {}
Dictionary is empty

参考：https://docs.oracle.com/javase/7/docs/api/java/util/Dictionary.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 Dictionary 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。