Java Arrays binarySearch() Method

Description

The Java Arrays binarySearch(char[] a, char key) method searches the specified array of chars for the specified value using the binary search algorithm. The array 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(char[] a, char key) method

public static int binarySearch(char[] a, char key)

Parameters

  • a − This is the array 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 greater than the key, or a.length if all elements in the array are less than the specified key.

Exception

NA

Java Arrays binarySearch(char[] a, int fromIndex, int toIndex, char key) Method

Description

The Java Arrays binarySearch(char[] a, int fromIndex, int toIndex, char key) method searches a range of the specified array of chars 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(char[] a, int fromIndex, int toIndex, char key) method

public static int binarySearch(char[] a, int fromIndex, int toIndex, char 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

Performing Binary Search on char Array Example

The following example shows the usage of Java Arrays binarySearch(char[], key) method. First, we've created an array of chars, sorted and printed them. Then binary search is performed on a value and result is printed.

package com.tutorialspoint;
import java.util.Arrays;
public class ArrayDemo {
   public static void main(String[] args) {

      // initializing unsorted char array
      char charArr[] = {'a', 'c', 'b', 'e','d'};

      // sorting array
      Arrays.sort(charArr);

      // let us print all the elements available in list
      System.out.println("The sorted char array is:");
      for (char ch : charArr) {
         System.out.println("Char = " + ch);
      }

      // entering the value to be searched
      char searchVal = 'e';
      int retVal = Arrays.binarySearch(charArr,searchVal);
      System.out.println("The index of element e is : " + retVal);
   }
}

Output

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

The sorted char array is:
Char = a
Char = b
Char = c
Char = d
Char = e
The index of element e is : 4

Performing Binary Search on char Sub-Array Example

The following example shows the usage of Java Arrays binarySearch(char[], fromIndex, toIndex, key) method. First, we've created an array of chars, sorted and printed them. Then binary search is performed on a value on sub array and result is printed.

package com.tutorialspoint;
import java.util.Arrays;
public class ArrayDemo {
   public static void main(String[] args) {

      // initializing unsorted char array
      char charArr[] = {'a', 'c', 'b', 'e','d'};

      // sorting array
      Arrays.sort(charArr);

      // let us print all the elements available in list
      System.out.println("The sorted char array is:");
      for (char ch : charArr) {
         System.out.println("Char = " + ch);
      }

      // entering the value to be searched
      char searchVal = 'e';

      // entering the range of index
      int retVal = Arrays.binarySearch(charArr,2,5,searchVal);
      System.out.println("The index of element e is : " + retVal);
   }
}

Output

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

The sorted char array is:
Char = a
Char = b
Char = c
Char = d
Char = e
The index of element e is : 4

Performing Binary Search on char Array for Non-Existent Value Example

The following example shows the usage of Java Arrays binarySearch(char[], key) method. First, we've created an array of chars, sorted and printed them. Then binary search is performed on a value which is not present in the array and result is printed .

package com.tutorialspoint;
import java.util.Arrays;
public class ArrayDemo {
   public static void main(String[] args) {

      // initializing unsorted char array
      char charArr[] = {'a', 'c', 'b', 'e','d'};

      // sorting array
      Arrays.sort(charArr);

      // let us print all the elements available in list
      System.out.println("The sorted char array is:");
      for (char ch : charArr) {
         System.out.println("Char = " + ch);
      }

      // entering the value to be searched
      char searchVal = 'f';
      int retVal = Arrays.binarySearch(charArr,searchVal);
      System.out.println("The index of element f is : " + retVal);
   }
}

Output

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

The sorted char array is:
Char = a
Char = b
Char = c
Char = d
Char = e
The index of element f is : -6
java_util_arrays.htm
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