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Perform Binary Search on ArrayList with Java Collections
In order to perform Binary Search on ArrayList with Java Collections, we use the Collections.binarySearch() method.
Declaration −The java.util.Collections.binarySearch() method is declared as follows −
public static int binarySearch(List list, T key)
The above method returns the position of the key in the list sorted in ascending order. If we use a Comparator c to sort the list, the binarySearch() method will be declared as follows −
public static int binarySearch(List list, T key, Comparator c)
If key is not present, the it returns ((insertion point) + 1) *(-1).
Let us see a program to perform binarySearch() on ArrayList −
Example
import java.util.*;
public class Example {
public static void main (String[] args) {
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(1);
list.add(2);
list.add(7);
int pos = Collections.binarySearch(list, 1); // 1 is present at 0th index
System.out.println(pos);
pos = Collections.binarySearch(list, 5);
/* since 5 is not present and it would be inserted at index 2
the method returns (-1)*() */
System.out.println(pos);
}
}Output
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Updated on: 25-Jun-2020
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