get index of element in list java code example

Example 1: ArrayList indexOf(Object o) method in java

import java.util.ArrayList;
public class ArrayListIndexOfMethodExample
{
   public static void main(String[] args)
   {
      ArrayList<Integer> al = new ArrayList<Integer>(5);
      al.add(8);
      al.add(6);
      al.add(5);
      al.add(7);
      al.add(9);
      System.out.print("ArrayList values are: ");
      for(Integer num : al)
      {
         System.out.print(num);
         System.out.print(" ");
      }
      // indexOf() method to find index of 5
      int position = al.indexOf(5);
      System.out.println("\nElement 5 is at index: " + position);
   }
}

Example 2: get index of element in array java

System.out.println(new String(list).indexOf("e"));

Example 3: get index of an array element java

public class Exercise6 {
       public static int  findIndex (int[] my_array, int t) {
        if (my_array == null) return -1;
        int len = my_array.length;
        int i = 0;
        while (i < len) {
            if (my_array[i] == t) return i;
            else i=i+1;
        }
        return -1;
    }
    public static void main(String[] args) {
      int[] my_array = {25, 14, 56, 15, 36, 56, 77, 18, 29, 49};
      System.out.println("Index position of 25 is: " + findIndex(my_array, 25));
      System.out.println("Index position of 77 is: " + findIndex(my_array, 77));
       }
}