Java Collections binarySearch() Method

❮ Collections Methods

import java.util.ArrayList;
import java.util.Collections;

public class Main {
  public static void main(String[] args) {
    ArrayList<String> cars = new ArrayList<String>();
    cars.add("Volvo");
    cars.add("BMW");
    cars.add("Ford");
    cars.add("Mazda");
    Collections.sort(cars);
    System.out.println(cars);
    System.out.println(Collections.binarySearch(cars, "Ford"));
  }
}

Definition and Usage

The binarySearch() method searches a list for an item and returns its index (position). It uses binary search (a fast search that splits the list in half again and again), so the list must be sorted first.

If the item is not found, the method returns a negative number.

Tip: Use Collections.sort() before you search. If the list is not sorted, the result can be wrong.

Syntax

One of the following:

public static int binarySearch(List<T> list, T key)

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

T refers to the data type of items in the list.

Parameter Values

Technical Details

Related Pages

Java Collections Framework Tutorial

Java Sort a List Tutorial