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?cái)?shù)(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(gè)靜態(tài)方法，因此可以使用類名進(jìn)行訪問，如果嘗試使用類對(duì)象訪問該方法，那么也不會(huì)收到錯(cuò)誤。

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

  frequency()方法在返回頻率時(shí)可能會(huì)引發(fā)異常。

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

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

Syntax:

句法：

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

Parameter(s):

參數(shù)：

• 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(jì)算給定對(duì)象(obj)頻率的Collection對(duì)象。

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

  對(duì)象obj –表示要計(jì)算其頻率的對(duì)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(duì)象相對(duì)于給定集合的頻率。

Example:

例：

// Java program is to demonstrate the example // of int frequency() of Collectionsimport 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 listlink_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 LinkedListSystem.out.println("link_l: " + link_l);System.out.println();// By using frequency() method is to// return the object frequency of the// given collection linked istint f1 = Collections.frequency(link_l, 40);int f2 = Collections.frequency(link_l, 30);// Display frequencySystem.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

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