哈希表包含 Java 中的()方法
原文:https://www . geesforgeks . org/hashtable-contains-method-in-Java/
java 中的 Java . util . Hashtable . contains(Object value)方法用于检查哈希表中存在的任何键是否正在映射特定的值。
语法:
Hash_table.contains(*Object value*)
参数:该方法接受一个对象类型的参数值，并引用映射待验证的哈希表的值。
返回值:如果传递的值由哈希表中的任意键映射，则该方法返回布尔真值。
异常:如果传递的值为空，则该方法抛出空指针异常。
以下程序说明上述方法的工作: 程序 1:
// Java code to illustrate the contains() method
import java.util.*;
public class Hash_Table_Demo {
public static void main(String[] args)
{
// Creating an empty Hashtable
Hashtable<Integer, String> hash_table =
new Hashtable<Integer, String>();
// Mapping string values to int keys
hash_table.put(10, "Geeks");
hash_table.put(15, "4");
hash_table.put(20, "Geeks");
hash_table.put(25, "Welcomes");
hash_table.put(30, "You");
// Displaying the HashMap
System.out.println("Initial Table is: " + hash_table);
// Checking for the Value 'Geeks'
System.out.println("Is the value 'Geeks' present? " +
hash_table.contains("Geeks"));
// Checking for the Value 'World'
System.out.println("Is the value 'World' present? " +
hash_table.contains("World"));
}
}
Output:
Initial Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}
Is the value 'Geeks' present? true
Is the value 'World' present? false
程序 2:
// Java code to illustrate the contains() method
import java.util.*;
public class Hash_Table_Demo {
public static void main(String[] args)
{
// Creating an empty Hashtable
Hashtable<String, Integer> hash_table =
new Hashtable<String, Integer>();
// Mapping int values to string keys
hash_table.put("Geeks", 10);
hash_table.put("4", 15);
hash_table.put("Geeks", 20);
hash_table.put("Welcomes", 25);
hash_table.put("You", 30);
// Displaying the Hashtable
System.out.println("Initial Mappings are: " + hash_table);
// Checking for the Value '10'
System.out.println("Is the value '10' present? " +
hash_table.containsValue(10));
// Checking for the Value '30'
System.out.println("Is the value '30' present? " +
hash_table.containsValue(30));
// Checking for the Value '40'
System.out.println("Is the value '40' present? " +
hash_table.containsValue(40));
}
}
Output:
Initial Mappings are: {You=30, Welcomes=25, 4=15, Geeks=20}
Is the value '10' present? false
Is the value '30' present? true
Is the value '40' present? false
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