MTG mana base estimator — code from http://www.channelfireball.com/articles/frank-analysis-how-many-colored-mana-sources-do-you-need-to-consistently-cast-your-spells/

mana.java

package manabase;

import java.util.Arrays.*;
import java.util.Random;

public class ManaBase {

    public static void main(String[] args) {

        Deck deck=new Deck();
        int NrIterations=1000000;
        int NrGoodLandsNeeded=2;
        int TurnAllowed=2;
        int NrCards=99;
        int NrLands=40;
        int CardType;
        int LandsInHand;
        int GoodLandsInHand;
        boolean Mulligan;
        
        for (int NrGoodLands=6; NrGoodLands<=24; NrGoodLands++){
            
            double CountOK=0.0;
            double CountConditional=0.0;
            
            for (int i=1; i<=NrIterations; i++){
                
                //Draw opening 7
                deck.SetDeck(NrLands, NrGoodLands, NrCards);
                LandsInHand=0;
                GoodLandsInHand=0;
                for (int j=1; j<=7; j++){
                    CardType=deck.DrawCard();
                    if (CardType<3) {LandsInHand++;}
                    if (CardType==1) {GoodLandsInHand++;}   
                }
                Mulligan=false;
                if (LandsInHand<2) {Mulligan=true;}
                if (LandsInHand>5) {Mulligan=true;}
               
                //Mulligan to 6
                if (Mulligan){
                    deck.SetDeck(NrLands, NrGoodLands, NrCards);
                    LandsInHand=0;
                    GoodLandsInHand=0;
                    for (int j=1; j<=6; j++){
                        CardType=deck.DrawCard();
                        if (CardType<3) {LandsInHand++;}
                        if (CardType==1) {GoodLandsInHand++;}   
                    }
                    Mulligan=false;
                    if (LandsInHand<2) {Mulligan=true;}
                    if (LandsInHand>4) {Mulligan=true;}
                }
                
                //Mulligan to 5
                if (Mulligan){
                    deck.SetDeck(NrLands, NrGoodLands, NrCards);
                    LandsInHand=0;
                    GoodLandsInHand=0;
                    for (int j=1; j<=5; j++){
                        CardType=deck.DrawCard();
                        if (CardType<3) {LandsInHand++;}
                        if (CardType==1) {GoodLandsInHand++;}   
                    }
                    Mulligan=false;
                    if (LandsInHand<1) {Mulligan=true;}
                    if (LandsInHand>4) {Mulligan=true;}
                }
                
                //Mulligan to 4
                if (Mulligan){
                    deck.SetDeck(NrLands, NrGoodLands, NrCards);
                    LandsInHand=0;
                    GoodLandsInHand=0;
                    for (int j=1; j<=4; j++){
                        CardType=deck.DrawCard();
                        if (CardType<3) {LandsInHand++;}
                        if (CardType==1) {GoodLandsInHand++;}   
                    }
                }
                
                //Draw cards for the number of turns available
                for (int turn=1; turn<=TurnAllowed-1; turn++){
                    CardType=deck.DrawCard();
                    if (CardType<3) {LandsInHand++;}
                    if (CardType==1) {GoodLandsInHand++;}   
                }
                
                if (GoodLandsInHand>=NrGoodLandsNeeded) {CountOK++;}
                if (LandsInHand>=NrGoodLandsNeeded) {CountConditional++;}
                
            } // end of 1000000 iterations
            
            System.out.println("With "+NrGoodLands+" good lands: Prob="+CountOK/CountConditional);
        }
    }
    
}

class Deck {
    int NumberOfLands;
    int NumberOfGoodLands;
    int NumberOfCards;
 
    void SetDeck (int NrLands, int NrGoodLands, int NrCards) {
        NumberOfLands=NrLands;
        NumberOfGoodLands=NrGoodLands;
        NumberOfCards=NrCards;
    }
   
    int DrawCard (){
            Random generator = new Random();
            int RandomIntegerBetweenOneAndDeckSize=generator.nextInt( this.NumberOfCards)+1;
            int CardType=0;
            int GoodLandCutoff=NumberOfGoodLands;
            int LandCutoff=NumberOfLands;
           
            if (RandomIntegerBetweenOneAndDeckSize<=GoodLandCutoff) {CardType=1; this.NumberOfGoodLands--; this.NumberOfLands--; this.NumberOfCards--;}
            if (RandomIntegerBetweenOneAndDeckSize>GoodLandCutoff && RandomIntegerBetweenOneAndDeckSize<=LandCutoff) {CardType=2; this.NumberOfLands--; this.NumberOfCards--;}
            if (RandomIntegerBetweenOneAndDeckSize>LandCutoff) {CardType=3; this.NumberOfCards--;}
            return CardType;
    }
}