Java IdentityHashMap clear()方法

Java中的java.util.IdentityHashMap.clear()方法是用来清除和删除指定地图中的所有元素或映射的。

语法

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。

下面的程序用来说明java.util.IdentityHashMap.clear()方法的工作。

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： 同样的操作可以在任何类型的Mapping中进行，不同数据类型的变化和组合。