Java 字典 remove()方法

Dictionary类的 remove() 方法接受一个键作为参数，并删除映射到该键的相应值。

语法

public abstract V remove(Object key)

参数： 该函数接受一个参数 key ，表示要从 dictionary 中删除的 key 及其映射。

返回值： 该函数返回映射到 该键 的值，如果 该键 没有映射，则返回 NULL。

异常： 如果作为参数传递的 key 是NULL，该函数不会抛出 NullPointerException 。

下面的程序说明了 java.util.Dictionary.remove() 方法的使用。

程序1 :

// Java Program to illustrate
// java.util.Dictionary.remove() 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);
  
        // Display the removed value
        System.out.println(d.remove(3)
                           + " has been removed");
  
        // Print the Dictionary
        System.out.println("\nDictionary: " + d);
    }
}

输出。

Dictionary: {3=Geeks, 2=for, 1=Geeks}
Geeks has been removed

Dictionary: {2=for, 1=Geeks}

程序2 。

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

输出。

Dictionary: {b=gfg, a=GFG}
GFG has been removed
gfg has been removed

Dictionary: {}
Dictionary is empty

**参考资料: ** https://docs.oracle.com/javase/7/docs/api/java/util/Dictionary.html#remove()