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Java Collections binarySearch() Method

The binarySearch() is an inbuilt method of Java Collections class which returns the position of the object in a sorted list. There are two different types of Java collections binarySearch() method which can be differentiated depending on its parameter.

These are:

  1. Java Collections binarySearch(List<? extends Comparable<? super T>> list, T key)
  2. Java Collections binarySearch(List<? extends T> list, T key, Comparator<? super T> c)

Java Collections binarySearch(List<? extends Comparable<? super T>> list, T key)

This method is used to search the provided list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the specified natural number, prior to making the method call. If the list is not sorted, the results are undefined.

Java Collections binarySearch(List<? extends T> list, T key, Comparator<? super T> c)

This method is used to search the provided list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the specified comparator prior to making the method call.

Syntax

Following is the declaration of binarySearch() method:

Parameter

Parameter Description Required/Optional
list It is specified by user to be searched. Required
key It is the key to be searched for in the provided list. Required
c It is a comparator used for sorting the list. Required

Returns

Method Returns
binarySearch(List<? extends Comparable<? super T>> list, T key) It returns the index of the key in a sorted list of an ascending order.
binarySearch(List<? extends T> list, T key, Comparator<? super T> c) It returns the index of the key in a sorted list of an order defined by comparator c.

Exceptions

ClassCastException- It throws exception if the elements of the list are not mutually comparable or the search key is not mutually comparable with the elements of the list.

Compatibility Version

Java 1.5 and above

Example 1

Test it Now

Output:

index 'D' is available at position: 3

Example 2

Test it Now

Output:

Provided List are: [10, -20, 30, -40, 50]
Index '-20' is available at position: -4

Example 3

Test it Now

Output:

Provided List are: [10, -20, 30]
Enter the search key: D
Exception in thread "main" java.lang.ClassCastException: java.base/java.lang.Integer cannot be cast to java.base/java.lang.String
	at java.base/java.lang.String.compareTo(String.java:124)
	at java.base/java.util.Collections$ReverseComparator.compare(Collections.java:5140)
	at java.base/java.util.Collections$ReverseComparator.compare(Collections.java:5131)
	at java.base/java.util.Collections.indexedBinarySearch(Collections.java:333)
	at java.base/java.util.Collections.binarySearch(Collections.java:321)
	at myPackage.CollectionBinarySearchExample3.main(CollectionBinarySearchExample3.java:16)

Example 4

Test it Now

Output:

4 is available at index: 3

Example 5

Test it Now

Output:

Available at index: 0
Found at index: -1





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