How to search element in Integer Array using Index in Java?

Declaration :

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

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

Explanation :

Purpose	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.
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

Java Program : Example

Below example will explain java.util.Arrays.binarySearch() method.

package com.c4learn;
import java.util.Arrays;
public class ArrayDemo {
public static void main(String[] args) {
		    // Initialize unsorted int array
		    int arr[] = {30,20,10,40,50};
		    // Sorting array
		    Arrays.sort(arr);
		    // Printing the sorted int array list
		    System.out.println("The sorted int array is:");
		    for (int num : arr) {
		      System.out.println("Array Element is " + num);
		    }
		    // Enter the value to be searched
		    int Val = 20;
		    // Enter range of index
		    int retVal = Arrays.binarySearch(arr,0,5,Val);
		    System.out.println("The index of element 20 is : " + retVal);
		  }	   
}

package com.c4learn;

import java.util.Arrays;

public class ArrayDemo {

public static void main(String[] args) {

// Initialize unsorted int array

int arr[] = {30,20,10,40,50};

// Sorting array

Arrays.sort(arr);

// Printing the sorted int array list

System.out.println("The sorted int array is:");

for (int num : arr) {

System.out.println("Array Element is " + num);

}

// Enter the value to be searched

int Val = 20;

// Enter range of index

int retVal = Arrays.binarySearch(arr,0,5,Val);

System.out.println("The index of element 20 is : " + retVal);

}

Output of Program :

The sorted int array is:
Array Element is 10
Array Element is 20
Array Element is 30
Array Element is 40
Array Element is 50
The index of element 20 is : 1

The sorted int array is:

Array Element is 10

Array Element is 20

Array Element is 30

Array Element is 40

Array Element is 50

The index of element 20 is : 1

Table of Content