Java中的java.util.IdentityHashMap.keySet() 方法用于创建哈希映射中包含的关键元素的集合。它基本上返回键的集合,或者我们可以创建一个新的集合并将关键元素存储在其中。

句法:

Identity_Hash_Map.keySet()

参数:该方法不带任何参数。

返回值:该方法返回一个具有IdentityHashMap键的集合。

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

程序1:将字符串值映射到整数键。

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

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

        // Creating an empty IdentityHashMap
        Map<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);

        // Using keySet() to get the set view of keys
        System.out.println("The set is: " + Identity_hash.keySet());
    }
}

输出:

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
The set is: [30, 15, 10, 25, 20]

程序2:将整数值映射到字符串键。

// Java code to illustrate the keySet() 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);

        // Using keySet() to get the set view of keys
        System.out.println("The set is: " + Identity_hash.keySet());
    }
}

输出:

Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
The set is: [Welcomes, 4, You, Geeks]

 
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