java - Generic Binary Search Using String -

i have generic binary search functions integers in array. however, when applied array of strings return @ 3 of indexes correctly ([1],[2],[3]), while marking others nonexistent ([-1]). in advance insight.

public class binarysearch {  private binarysearch() { }  private static <t extends comparable<? super t>> int search(t[] list, int first, int last, t key){     int foundposition;     int mid = first + (last - first) / 2;       if (first > last)         foundposition = -1;     else if (key.equals(list[mid]))         foundposition = mid;     else if (key.compareto(list[mid]) < 0)         foundposition = search(list, first, mid - 1, key);     else         foundposition = search(list, mid + 1, last, key);     return foundposition; }   public static void main(string args[]) {     //integer     integer [] searchinteger = {0,2,4,6,8,10,12,14,16};     int integerlast = searchinteger.length-1;     system.out.println("integer test array contains...");         (integer a1 : searchinteger) {          system.out.print(a1 + " ");         }     system.out.println("\nchecking integer array...");     int result;     (int key = -4; key < 18; key++) {         result = binarysearch.search(searchinteger, 0, integerlast, key);         if (result < 0)             system.out.println(key + " not in array.");         else             system.out.println(key + " @ index " + result + ".");         }     //string     string[] searchfruits = {"lemon", "apple", "banana", "peach", "pineapple", "grapes", "blueberry", "papaya"};           system.out.println("string test array contains...");     (string a1 : searchfruits) {         system.out.print(a1 + " ");     }     system.out.println("\nchecking string array...");     int results;     int fruitlast = searchfruits.length-1;     (int key = 0; key < searchfruits.length; key++){         results = binarysearch.search(searchfruits, 0, fruitlast, searchfruits[key]);         system.out.println("key = " + searchfruits[key]);         system.out.println("index result = " + results);         if (results < 0)             system.out.println(searchfruits[key] + " not in array.");         else             system.out.println(searchfruits[key] + " @ index " + results + ".");             } } } 

because string array

    string[] searchfruits = {"lemon", "apple", "banana", "peach", "pineapple", "grapes", "blueberry", "papaya"};  

is not sorted, integer array

  integer [] searchinteger = {0,2,4,6,8,10,12,14,16}; 

is sorted.

by way have used arrays.binarysearch() too.