java - How to generate unique random numbers? -

i trying solve problem.i have define array 5 elements on , define random generator method 3 defined integersi1,i2,i3 different each other.so when variables generated have different .i hope clear.can please me ,or suggestion welcome.

import java.util.*;   public class array {      public static void main(string[] arg) {         int[] v = { 1, 2, 3, 4, 5 };         displayarray(v);         array n = new array();          n.randomgenerator();     }      private static void displayarray(int[] arr) {         (int x : arr)             system.out.print(x + " ");         system.out.println();     }      public int[] randomgenerator() {          int[] = new int[3];         int i1;         int i2;         int i3;          (int = 0; < a.length; i++) {             a[i] = (int) (math.random() * 5);         }         i1 = a[0];         i2 = a[1];         i3 = a[2];          if (i1 != i2 && i2 != i3 && i1 != i3) {             system.out.println(i1 + "," + i2 + "," + i3);         } else {             if (i1 == i2 && i2 == i3 && i1 == i3) {              }         }          return a;     } } 

there 2 options using this:

one possibility while generating new random number check if it's of existing random numbers , if so, retry generation. in theory, take long amount of time in practice it's fast.

another option e.g. if want generate random numbers in range 0-9 (inclusive-inclusive) , if have e.g. 3 , 7, generate math.random()%8 instead of math.random()%10 , if number greater or equal 3, increment one, , if new number greater or equal 7, increment one.