CODEWITHSUNDEEP
javaarrays2d
Newbie
Newbie

Reputation: 3

Using Number Randoms in Arrays that randomize

I am making a small class for a little project. It's a text based RPG game and I am trying to create a drop class for when NPC's die. I have create a couple Math.random methods (which are exactly the same, just differently named for my convenience.) to drop random amounts for an item id (name) and to get the rarity of the item dropped. It all works fine, but it only randomizes one time (on startup or run) and it won't randomize the amounts after that. I am also randomizing it between 2 numbers, for example, 25 and 50, the random not going lower then 25 or higher then 50.

My question is: How can I randomize a integer in a 2D Array or a general array after each time a NPC dies, so the random number that is first obtained changes and doesn't stay the same. Because right now, it stays at the number choose. if the number is 25, then the next npc I kill, the amount would still be 25.. and 25.. and 25.. and so on. I need it to randomize or change.

Please help, thank you.

   public class DropConfig {

    private static final int
        ALWAYS = 0,
        VERY_COMMON = rate(1, 9),
        COMMON = rate(10, 20),
        UNCOMMON = rate(30, 40),
        RARE = rate(50, 60),
        VERY_RARE = rate(70, 80),
        SUPER_RARE = rate(90, 100);

    public static final int[][] NPC_DROPS = {

        // Normal NPC's
        {1, 526, 1, ALWAYS}, 
        {2, 526, 1, ALWAYS}, 
        {3, 526, 1, ALWAYS}, 
        {1, 995, drop(1, 50), ALWAYS}, 
        {2, 995, drop(1, 50), ALWAYS},
        {3, 995, drop(1, 50), ALWAYS},

        // Moderate NPC's
        {9, 526, 1, ALWAYS}, 
        {9, 995, drop(250, 500), UNCOMMON},
        {9, 555, drop(2, 7), VERY_COMMON},
        {9, 995, drop(5, 50), VERY_COMMON},
        {9, 1050, 1, RARE}, 
    };

    public static int rate(int min, int max) {
        return 1 + (int)(Math.random() * ((max - min) + 1));
    }

    //Same as rate, different name for looks.
    public static int drop(int min, int max) {
        return 1 + (int)(Math.random() * ((max - min) + 1));
    }

Heres where I call the drops method

public void npcDeath() {
    int npc = 0;    
    if (npc == null)
        return;
    for(npc = 0; npc < DropConfig.NPC_DROPS.length; npc++) {
        if(npc == DropConfig.NPC_DROPS[npc][0]) {
            if(Misc.random(DropConfig.NPC_DROPS[npc][3]) == 0) { //Drops ALWAYS item
                Item(DropConfig.NPC_DROPS[npc][1], DropConfig.NPC_DROPS[npc][2]);
            }
        }
    }
}

Upvotes: 0

Views: 209

Answers (3)

user1367351
user1367351

Reputation: 102

Creating an instance of Random with the same seed you will get the same 'random' number. Have you considered using SecureRandom? The difference between SecureRandom and Random is that SecureRandom produces non-deterministic output on each call.

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533530

You want to place functions as constants. You can do this in a language like Scala naturally, but in Java you have to work a little harder.

In every case, you need to call a function to get the actual value.

You can use enum and anonymous methods, but the simplest way/hack is to encode your ranges.

public static int rate(int min, int max) { // same for drop.
    int range = max - min;
    return (range << 16) | (min & 0xFFFF);
}

public static int eval(int minMax) {
    int min = (short) minMax;
    int range = (short) (minMax >> 16);
    if (range == 0)
       return min; // plain number.
    else
       return min + (int) (Math.random() * (range + 1));
}

You need to call eval() to turn your encoded range into a random number.

Upvotes: 0

JB Nizet
JB Nizet

Reputation: 691755

If I understand correctly, you would like the elements of the NPC_DROPS array initialized with a call to drop() to be reinitialized each time this NPC_DROPS array is used.

Well, NPC_DROPS is a constant, so it can't change. Generate it each time it's accessed, using a method:

public static int[][] generateNpcDrops(){
    return new int[][] {

    // Normal NPC's
    {1, 526, 1, ALWAYS}, 
    {2, 526, 1, ALWAYS}, 
    {3, 526, 1, ALWAYS}, 
    {1, 995, drop(1, 50), ALWAYS}, 
    {2, 995, drop(1, 50), ALWAYS},
    {3, 995, drop(1, 50), ALWAYS},

    // Moderate NPC's
    {9, 526, 1, ALWAYS}, 
    {9, 995, drop(250, 500), UNCOMMON},
    {9, 555, drop(2, 7), VERY_COMMON},
    {9, 995, drop(5, 50), VERY_COMMON},
    {9, 1050, 1, RARE}, 
    }
}

...

public void npcDeath() {
    int npc = 0;    
    if (npc == null)
        return;
    int[][] npcDrops = DropConfig.generateNpcDrops();
    for(npc = 0; npc < npcDrops.length; npc++) {
        if(npc == npcDrops[npc][0]) {
            if(Misc.random(npcDrops[npc][3]) == 0) { //Drops ALWAYS item
                Item(c, npcDrops[npc][1], npcDrops[npc][2]);
            }
        }
    }
}

Upvotes: 1

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