I have an int array and I have assigned a value from it with a random index to a int variable. I wanted to know if there is a way to check the index from the array that it came from from the variable it was assigned.
Random rand = new Random();
private int[] cards = {2, 3, 4, 5, 6, 7, 8, 9, 10};
int a = cards[rand.nextInt(8)];
so I assigned a value from the array to variable a but I want to know if there is a way to check the variable a to see what the index was it came from
You can store the value of random before the use.
int randomValue = rand.nextInt(8);
int a = cards[randomValue];
You know the index number as you are already getting the value in the index position of the array.
int index = rand.nextInt(8);
It is always advised to use ArrayList. And if you had used that there is an easy method called "indexOf" to find out the index of the value in the list.
indexOf doesn't tell you where your element comes from, it just tells you where an "equal" instance (according to the equals implementation) is placed in the list. It could still be a different instance.
indexOf function from ArrayList gives you that choice.indexOf returns the first index where an equal object is located and equal is determined by the equals implementation. So this method might not return the index of the instance you're looking. For example: String a = new String("a"); String b = new String("a"); List<String> l = new ArrayList<>(Arrays.asList(a, b)); System.out.println(l.indexOf(b));. This prints "0", because on index 0 there is an equal instance, but is refers to a different object in the memory and is therefore not the one you're looking for, just a "similar" one.Try this:
int index= rand.nextInt(8);
int a = cards[index];
With a simple array, you have to iterate to find out what position a given value is in. For example:
int findSlot(int a)
{
for (int i = 0, n = cards.length; i < n; i++)
{
if (cards[i] == a) return i;
}
}
However, if you use an ArrayList, you can make use of the method indexOf().
As noted by other folks who've answered, the index returned (in both cases) will be the first matching instance.
rand.nextInt(8)in an own variable, then you know your index ... quite obvious, right?