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    Java中的java.util.IdentityHashMap.clear() 方法用于清除和删除指定映射中的所有元素或映射。

    句法:

    Identity_HashMap.clear()

    参数:该方法不接受任何参数。

    返回值:该方法不返回任何值。

    下面的程序用于说明java.util.IdentityHashMap.clear() 的工作方法

    程序1:将字符串值映射到整数键。

    // Java code to illustrate the clear() method
    import java.util.*;
     
    public class Identity_Hash_Map_Demo {
        public static void main(String[] args)
        {
     
            // Creating an empty IdentityHashMap
            IdentityHashMap<Integer, String> identity_hash = new IdentityHashMap<Integer, String>();
     
            // Mapping string values to int keys
            identity_hash.put(10, "Geeks");
            identity_hash.put(15, "4");
            identity_hash.put(20, "Geeks");
            identity_hash.put(25, "Welcomes");
            identity_hash.put(30, "You");
     
            // Displaying the IdentityHashMap
            System.out.println("Initial Mappings are: "
                               + identity_hash);
     
            // Clearing the map using clear()
            identity_hash.clear();
     
            // Displaying the final IdentityHashMap
            System.out.println("Final Map: "
                               + identity_hash);
        }
    }
    

    输出:

    Initial Mappings are: {10=Geeks, 30=You, 20=Geeks, 25=Welcomes, 15=4}
    Final Map: {}

    程序2:将 整数值映射到字符串键。

    // Java code to illustrate the clear() method
    import java.util.*;
     
    public class Identity_Hash_Map_Demo {
        public static void main(String[] args)
        {
     
            // Creating an empty IdentityHashMap
            Map<String, Integer> identity_hash = new IdentityHashMap<String, Integer>();
     
            // Mapping int values to string keys
            identity_hash.put("Geeks", 10);
            identity_hash.put("4", 15);
            identity_hash.put("Geeks", 20);
            identity_hash.put("Welcomes", 25);
            identity_hash.put("You", 30);
     
            // Displaying the IdentityHashMap
            System.out.println("Initial Mappings are: " + identity_hash);
     
            // Clearing the map using clear()
            identity_hash.clear();
     
            // Displaying the final IdentityHashMap
            System.out.println("Final Map: "
                               + identity_hash);
        }
    }
    

    输出:

    Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
    Final Map: {}

    注意:对于具有不同数据类型变体的和组合的任何类型的映射,都可以执行相同的操作。

     
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