arrays - default java util binary-search returns wrong results -

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• array.binarysearch returning wrong data 2 answers

i got strange behavior binary search in java util

this code

public static void main (string[] args) throws java.lang.exception {     // code goes here      int[] a={-1, 6, 3, 4, 7, 4} ;       for(int i=0;i<a.length;i++)      {          system.out.println(arrays.binarysearch(a,a[i])+"========="+a[i]);      } } 

should display values every element in array index

but works fine elements expect second 1

the returned values

0=========-1 -5=========6 2=========3 3=========4 4=========7 3=========4 

i tested on java 7 , java 8 , gave me same results

you can test online on https://ideone.com/7wmfgg

if read javadoc of binarysearch you'll see array must sorted :

/**  * searches specified array of longs specified value using  * binary search algorithm.  array must sorted (as  * {@link #sort(int[])} method) prior making call.  if  * not sorted, results undefined. ...