Implement rand7() using rand5()

public static int rand7() {
    int vals[][] = {
        { 1, 2, 3, 4, 5 },
        { 6, 7, 1, 2, 3 },
        { 4, 5, 6, 7, 1 },
        { 2, 3, 4, 5, 6 },
        { 7, 0, 0, 0, 0 }
    };
 
    int result = 0;
    while (result == 0)
    {
        int i = rand5();
        int j = rand5();
        result = vals[i-1][j-1];
    }
    return result;
}

Another approach is

public static int rand7() {
    while (true) {
        int num = 5 * (rand5() - 1) + (rand5() - 1);
        if (num < 21)
            return (num % 7 + 1);
    }
}