java.util.Collections.binarySearch() Method

---

---

Description

The binarySearch(List<? extends T>, T, Comparator<? super T>) method is used to search the specified list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the specified comparator.

Declaration

Following is the declaration for java.util.Collections.binarySearch() method.

public static <T> int binarySearch(List<? extends T> list,T key,Comparator<? super T> c)

Parameters

• list − This is the list to be searched.

• key − This is the key to be searched for.

• c − This is the comparator by which the list is ordered. A null value indicates that the elements' natural ordering should be used.

Return Value

The method call returns the index of the search key, if it is contained in the list.

Exception

ClassCastException − This is thrown if the list contains elements that are not mutually comparable using the specified comparator.

Example

The following example shows the usage of java.util.Collections.binarySearch()

package com.tutorialspoint;

import java.util.*;

public class CollectionsDemo {
   public static void main(String args[]) {
   
      // create arraylist       
      ArrayList<String> arlst = new ArrayList<String>();

      // populate the list
      arlst.add("TP");
      arlst.add("PROVIDES");
      arlst.add("QUALITY");
      arlst.add("TUTORIALS");

      // search for key 'TUTORIALS' with natural ordering
      int index = Collections.binarySearch(arlst, "TUTORIALS", null);     

      System.out.println("'TUTORIALS' is available at index: "+index);
   }    
}

Let us compile and run the above program, this will produce the following result.

'TUTORIALS' is available at index: 3