Java中的WeakHashMap remove()方法

java.util.WeakHashMap.remove()是WeakHashMap类的一种内置方法，用于从Map中删除任何特定键的映射。它基本上是删除Map中任意特定键的值。

语法：

Weak_Hash_Map.remove(Object key)

参数： 该方法需要一个参数key，它的映射将从Map中删除。

返回值： 如果存在该键，则该方法返回先前映射到指定键的值，否则该方法返回NULL。

下面的程序说明了java.util.WeakHashMap.remove()方法的工作方式：
程序1： 当传递一个存在的键。

// Java code to illustrate the remove() method
            import java.util.*;

            public class Weak_Hash_Map_Demo {
                public static void main(String[] args)
                {

                    // Creating an empty WeakHashMap
                    Map weak_hash = new 
                                               WeakHashMap();

                    // Mapping string values to int keys
                    weak_hash.put(10, "Geeks");
                    weak_hash.put(15, "4");
                    weak_hash.put(20, "Geeks");
                    weak_hash.put(25, "Welcomes");
                    weak_hash.put(30, "You");

                    // Displaying the WeakHashMap
                    System.out.println("Initial Mappings are: " + 
                                                    weak_hash);

                    // Removing the existing key mapping
                    String returned_value = 
                                              (String)weak_hash.remove(20);

                    // Verifying the returned value
                    System.out.println("Returned value is: " + 
                                                  returned_value);

                    // Displayin the new map
                    System.out.println("New map is: " + weak_hash);
                }
            }

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: Geeks
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes}

程序2： 当传递一个新的键。

// Java code to illustrate the remove() method
            import java.util.*;

            public class Weak_Hash_Map_Demo {
                public static void main(String[] args)
                {

                    // Creating an empty WeakHashMap
                    Map weak_hash = 
                                             new WeakHashMap();

                    // Mapping string values to int keys
                    weak_hash.put(10, "Geeks");
                    weak_hash.put(15, "4");
                    weak_hash.put(20, "Geeks");
                    weak_hash.put(25, "Welcomes");
                    weak_hash.put(30, "You");

                    // Displaying the WeakHashMap
                    System.out.println("Initial Mappings are: " + 
                                                        weak_hash);

                    // Removing the new key mapping
                    String returned_value = 
                                                 (String)weak_hash.remove(50);

                    // Verifying the returned value
                    System.out.println("Returned value is: " + 
                                                  returned_value);

                    // Displayin the new map
                    System.out.println("New map is: "+weak_hash);
                }
            }

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: null
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}

注意： 同样的操作可以使用不同的数据类型的变化和组合类型的映射执行。