Binary Search implementation in java?

Question

difference between static int binarySearch(Object[] key) and static int binarySearch(primitive[] key) Explain with code?

Vulpes · Answer

Where you use primitive[] in your post I assume you mean one of the overloads of Arrays.binarySearch that takes an array of one of the primitive types (byte short int long float double or char) as a parameter rather than an Object array. In both cases the array needs to be sorted first before applying the binarySearch method otherwise the results will be undefined. However this may not be possible with an Object[] as it could contain both strings and numbers which are not comparable with one another. So in that event you'd get an undefined result. Here's an example: import java.util.Arrays; public class BinarySearchDemo { public static void main(String[] args) { // create unsorted array of ints int ia[] = {10 2 7 8 4}; // sort it Arrays.sort(ia); // print its elements System.out.print(The sorted int array is : ); for (int i : ia) { System.out.print(  + i); } System.out.println(); // enter a value to look for int search = 7; int index = Arrays.binarySearch(ia search); System.out.println(The index of  + search +  is :  + index); // now create an Object array which includes a string Object[] oa = {hello 10 2 7 8 4}; // can't sort this without getting an exception so don't bother // print its elements System.out.print(The unsorted object array is : ); for (Object o : oa) { System.out.print(  + o); } System.out.println(); // look for 'search' again index = Arrays.binarySearch(ia search); System.out.println(The index of  + search +  is now :  + index); } } When I compiled and ran this the output was: The sorted int array is : 2 4 7 8 10 The index of 7 is : 2 The unsorted object array is : hello 10 2 7 8 4 The index of 7 is now : 2 The last line is of course wrong since 7 is at index 3 in the (unsorted) array.

Abhijeet Singh · Answer

Thank you so much Sir ... :)