java 方法 示例

集合類的frequency()方法 (Collections Class frequency() method)

• frequency() method is available in java.util package.

  frequency()方法在java.util包中可用。

• frequency() method is used to return the frequency of the given Object (obj) to the given Collection (co) or in other words, this method is used to return the number of elements in the given collection which is same as the given Object (obj).

  frequency()方法用于將給定Object(obj)的頻率返回給定Collection(co)，換句話說，該方法用于返回給定Collection中與給定Object相同的元素數(obj)。

• frequency() method is a static method, so it is accessible with the class name and if we try to access the method with the class object then also we will not get an error.

  frequency()方法是一個靜態方法，因此可以使用類名進行訪問，如果嘗試使用類對象訪問該方法，那么也不會收到錯誤。

• frequency() method may throw an exception at the time of returning frequency.

  frequency()方法在返回頻率時可能會引發異常。

  NullPointerException: This exception may throw when the given parameter Collection (co) if null exists.

  NullPointerException ：如果給定參數Collection(co)存在null，則可能引發此異常。

Syntax:

句法：

    public static int frequency(Collection co, Object obj);

Parameter(s):

參數：

• Collection co – represents the Collection object in which to calculate the frequency of the given Object (obj).

  Collection co –表示要在其中計算給定對象(obj)頻率的Collection對象。

• Object obj – represents the object whose frequency is to be calculated.

  對象obj –表示要計算其頻率的對象。

Return value:

返回值：

The return type of this method is int, it returns the frequency of the given object with respect to the given collection.

此方法的返回類型為int ，它返回給定對象相對于給定集合的頻率。

Example:

例：

// Java program is to demonstrate the example
// of int frequency() of Collections
import java.util.*;
public class Frequency {
public static void main(String args[]) {
// Instantiate a LinkedList   
List link_l = new LinkedList();
// By using add() method is to
// add elements in linked list
link_l.add(10);
link_l.add(20);
link_l.add(30);
link_l.add(40);
link_l.add(50);
link_l.add(40);
link_l.add(30);
// Display LinkedList
System.out.println("link_l: " + link_l);
System.out.println();
// By using frequency() method is to
// return the object frequency of the
// given collection linked ist
int f1 = Collections.frequency(link_l, 40);
int f2 = Collections.frequency(link_l, 30);
// Display frequency
System.out.println("Collections.frequency(link_l,40): " + f1);
System.out.println("Collections.frequency(link_l,30): " + f2);
}
}

Output

輸出量

link_l: [10, 20, 30, 40, 50, 40, 30]Collections.frequency(link_l,40): 2
Collections.frequency(link_l,30): 2

翻譯自: https://www.includehelp.com/java/collections-frequency-method-with-example.aspx

java 方法 示例