java - Generate random number without duplicate in certain range

Question

I'm currently creating an app and it will generate random numbers. So each time it will generate three numbers num1, num2 and num3. These number should not be duplicate. For example if num1 = 1 than num2 and num3 cannot be equal to 1. I've tried this code where it will display three different number ranging from 0-2. And its working. However I would want to generate random number ranging from 1-3, 2-4, 3-5 and so on. So how can I achieve this by using the code below. Please help me since I'm new to this. Thank you.

for(int i=0; i<images.length; i++)
{
        num[i] = (int)(Math.random()*3);

        if (i == 0)
        {
        if(num[i]== 0)
            images[i].setImageResource(R.drawable.zero);
        else if(num[i]==1)
            images[i].setImageResource(R.drawable.one);
        else
            images[i].setImageResource(R.drawable.two);
        }

        else
        {
            while (num[i] ==  num[i-1] || num[i] == num[0] )
                num[i] = (int)(Math.random()*3);


        if(num[i]==0)
            images[i].setImageResource(R.drawable.zero);
        else if(num[i]==1)
            images[i].setImageResource(R.drawable.one);
        else
            images[i].setImageResource(R.drawable.two);

        }
    }

Answer 1

Create a list if all numbers in the range, then shuffle the list:

List<Integer> numbers = new ArrayList<>();
// eg for range 3-5
for (int i = 3; i <= 5; i++)
    numbers.add(i);
Collections.shuffle(numbers);

Now use them in their new (random) order.

Unless your range is very large (millions) this will work fine.

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Java8 version:

List<Integer> numbers = IntStream.rangeClosed(3, 5).boxed().collect(Collectors.toList());
Collections.shuffle(numbers);