集合類binarySearch()方法 (Collections Class binarySearch() method)

Syntax:

句法：

public static int binarySearch(List l, Type key_ele);public static int binarySearch(List l, Type key_ele, Comparator com);

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

  binarySearch()方法在java.util包中可用。

• binarySearch(List l, Type key_ele) method is used to find the given object (key_ele) in the given list (l) with the help of binary search.

  binarySearch(List l，Type key_ele)方法用于在二進制搜索的幫助下在給定列表(l)中找到給定對象(key_ele)。

• binarySearch(List l, Type key_ele, Comparator com) method is used to find the given object (key_ele) in the given list (l) and the list must be sorted based on defined Comparator object.

  binarySearch(List l，Type key_ele，Comparator com)方法用于在給定列表(l)中查找給定對象(key_ele)，并且必須基于定義的Comparator對象對列表進行排序。

• These methods may throw an exception at the time of finding the given element.

  這些方法在查找給定元素時可能會引發異常。

  ClassCastException: This exception may throw when the given parameter List elements that are mutually incomparable.

  ClassCastException ：當給定的參數List元素彼此不可比較時，可能引發此異常。

• These are static methods and it is accessible with the class name and if we try to access these methods with the class object then also we will not get any error.

  這些是靜態方法，可以使用類名進行訪問，如果嘗試使用類對象訪問這些方法，則也不會出現任何錯誤。

Parameter(s):

參數：

• In the first case, "binarySearch(List l, Type key_ele)"

  在第一種情況下，“ binarySearch(List l，Type key_ele)”

  • List l – represents the list object.
  • 列表l –表示列表對象。
  • Type key_ele – represents the key element to be searched.
  • key_ele類型 –表示要搜索的關鍵元素。

• In the second case, "binarySearch(List l, Type key_ele, Comparator com)"

  在第二種情況下，“ binarySearch(List l，Type key_ele，Comparator com)”

  • List l – represents the list object.
  • 列表l –表示列表對象。
  • Type key_ele – represents the key element to be searched.
  • key_ele類型 –表示要搜索的關鍵元素。
  • Comparator com – represents the Comparator object and we set the value to null that means it is natural or default order.
  • Comparator com –表示Comparator對象，我們將值設置為null表示它是自然順序或默認順序。

Return value:

返回值：

In both the cases, the return type of the method is int, it returns the position of the given key_ele(key element) when it exists in the given list.

在這兩種情況下，該方法的返回類型均為int ，當它存在于給定列表中時，它將返回給定key_ele(key元素)的位置。

Example:

例：

// Java program to demonstrate the example // of binarySearch() method of Collectionsimport java.util.*;public class BinarySearchOfCollections {public static void main(String args[]) {// Instantiates an array list objectList < Integer > arr_l = new ArrayList < Integer > ();// By using add() method is to add// objects in an array listarr_l.add(20);arr_l.add(10);arr_l.add(40);arr_l.add(30);arr_l.add(50);// Display ArrayListSystem.out.println("ArrayList: " + arr_l);// By using binarySearch(arr_l,30,null) method is// to search the the given object 30 in an arr_l// based on defined comparator object (null) and// here we are using null so list must be sorted// in an ascending orderint indices = Collections.binarySearch(arr_l, 30, null);// Display indicesSystem.out.println("Collections.binarySearch(arr_l,30,null): " + indices);// By using binarySearch(arr_l,30) method is// to search the the given object 30 in an arr_l// so list must be sorted in an natural or ascending orderindices = Collections.binarySearch(arr_l, 30);// Display indicesSystem.out.println("Collections.binarySearch(arr_l,30): " + indices);} }

Output

輸出量

ArrayList: [20, 10, 40, 30, 50] Collections.binarySearch(arr_l,30,null): -3 Collections.binarySearch(arr_l,30): -3

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

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