Java中的 ConcurrentHashMap keys() 方法及示例
Java中ConcurrentHashMap 类的keys()方法用于获取哈希图中存在的键的枚举。
句法:
Enumeration enu = ConcurrentHashMap.keys()
参数:该方法不带任何参数。
返回值:该方法返回 ConcurrentHashMap 的键的枚举。
下面的程序用于说明 keys() 方法的工作:
方案一:
// Java code to illustrate the keys() method
import java.util.*;
import java.util.concurrent.*;
public class ConcurrentHashMapDemo {
public static void main(String[] args)
{
// Creating an empty ConcurrentHashMap
ConcurrentHashMap
hash_map = new ConcurrentHashMap();
// Inserting elements into the map
hash_map.put(10, "Geeks");
hash_map.put(15, "4");
hash_map.put(20, "Geeks");
hash_map.put(25, "Welcomes");
hash_map.put(30, "You");
// Displaying the ConcurrentHashMap
System.out.println("The Map is: " + hash_map);
// Creating an empty enumeration to store
Enumeration enu = hash_map.keys();
System.out.println("The enumeration of keys are:");
// Displaying the Enumeration
while (enu.hasMoreElements()) {
System.out.println(enu.nextElement());
}
}
}
输出:
The Map is: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The enumeration of keys are:
20
25
10
30
15
方案二:
// Java code to illustrate the keys() method
import java.util.*;
import java.util.concurrent.*;
public class ConcurrentHashMapDemo {
public static void main(String[] args)
{
// Creating an empty ConcurrentHashMap
ConcurrentHashMap
hash_map = new ConcurrentHashMap();
// Inserting elements into the table
hash_map.put("Geeks", 10);
hash_map.put("4", 15);
hash_map.put("Geeks", 20);
hash_map.put("Welcomes", 25);
hash_map.put("You", 30);
// Displaying the ConcurrentHashMap
System.out.println("The Map is: " + hash_map);
// Creating an empty enumeration to store
Enumeration enu = hash_map.keys();
System.out.println("The enumeration of keys are:");
// Displaying the Enumeration
while (enu.hasMoreElements()) {
System.out.println(enu.nextElement());
}
}
}
输出:
The Map is: {4=15, Geeks=20, You=30, Welcomes=25}
The enumeration of keys are:
4
Geeks
You
Welcomes