Generating an array of random numbers without duplicates [duplicate]

Answer 1

Since you said without any libraries you could reimplement the Collections.shuffle(...) method for arrays.

int [] randoms = new int[5];

// creating an array containing the numbers 1-10
int [] shuffleArray = new int[10];
for (int i = 1; i <= 10; i++) {
    shuffleArray[i-1] = i;
}

// shuffling that array
Random random = new Random();
for (int i = 0; i < 10; i++) {
    int j = random.nextInt(10);
    int tmp = shuffleArray[i];
    shuffleArray[i] = shuffleArray[j];
    shuffleArray[j] = tmp;
}

// assigning the first 5 values to the random array
for (int i = 0; i < randoms.length; i++) {
    randoms[i] = shuffleArray[i];
}

Although i have to remark that Random needs an import too (needs a library too)