Java.util.Arrays.binarySearch() Method

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Description

The java.util.Arrays.binarySearch(int[] a, int fromIndex, int toIndex, int key) method searches a range of the specified array of ints for the specified value using the binary search algorithm. The range must be sorted before making this call.If it is not sorted, the results are undefined.

Declaration

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

public static int binarySearch(int[] a, int fromIndex, int toIndex, int key)

Parameters

  • a -- This is the array to be searched.

  • fromIndex -- This is the index of the first element (inclusive) to be searched.

  • toIndex -- This is the index of the last element (exclusive) to be searched.

  • key -- This is the value to be searched for.

Return Value

This method returns index of the search key, if it is contained in the array, else it returns (-(insertion point) - 1). The insertion point is the point at which the key would be inserted into the array; the index of the first element in the range greater than the key, or toIndex if all elements in the range are less than the specified key.

Exception

  • IllegalArgumentException -- if fromIndex > toIndex

  • ArrayIndexOutOfBoundsException -- if fromIndex < 0 or toIndex > a.length

Example

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

package com.tutorialspoint;

import java.util.Arrays;

public class ArrayDemo {
 
   public static void main(String[] args) {

    // initializing unsorted int array
    int intArr[] = {30,20,5,12,55};

    // sorting array
    Arrays.sort(intArr);

    // let us print all the elements available in list
    System.out.println("The sorted int array is:");
    for (int number : intArr) {
      System.out.println("Number = " + number);
    }

    // entering the value to be searched
    int searchVal = 12;

    // entering range of index
    int retVal = Arrays.binarySearch(intArr,1,3,searchVal);
	
    System.out.println("The index of element 12 is : " + retVal);
  }
}

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

The sorted int array is:
Number = 5
Number = 12
Number = 20
Number = 30
Number = 55
The index of element 12 is : 1



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