Question: Hello, I'm getting a logic error in my code here and I'm not sure what is going wrong. The language is Java. I'm supposed to
Hello,
I'm getting a logic error in my code here and I'm not sure what is going wrong. The language is Java. I'm supposed to be rolling a pair of dice 10000 times and recording the amount of times I get a pair of numbers (two 1's, two 2's etc.)
Here is my console output with the given code:
Number of rolls: 10000
Exception in thread "main" java.lang.NullPointerException
at edu.ilstu.DiceSimulationDriver.main(DiceSimulationDriver.java:41)
Here is my code:
DIE CLASS
import java.util.Random;
public class Die
{
private Random dice = new Random();
private int spots;
public Die(Random dice, int spots)
{
this.dice = dice;
this.spots = spots;
}
public void roll(Random dice)
{
spots = dice.nextInt(6) + 1;
}
public int getSpots()
{
return spots;
}
public boolean equals(Die other)
{
if(spots == other.getSpots())
{
return true;
}
return false;
}
}
DICE ACCUMULATOR CLASS
public class DiceAccumulator
{
private int snakeEyes;
private int twos;
private int threes;
private int fours;
private int fives;
private int sixes;
public void addSnakeEyes()
{
snakeEyes++;
}
public void addTwos()
{
twos++;
}
public void addThrees()
{
threes++;
}
public void addFours()
{
fours++;
}
public void addFives()
{
fives++;
}
public void addSixes()
{
sixes++;
}
public int getSnakeEyes()
{
return snakeEyes;
}
public int getTwos()
{
return twos;
}
public int getThrees()
{
return threes;
}
public int getFours()
{
return fours;
}
public int getFives()
{
return fives;
}
public int getSixes()
{
return sixes;
}
}
DICE SIMULATOR CLASS
public class DiceSimulator
{
DiceAccumulator diceA;
private int die1;
private int die2;
public DiceAccumulator runSimulation(int numRolls)
{
die1 = (int) (Math.random() * 6) + 1;
die2 = (int) (Math.random() * 6) + 1;
int spots = 0;
if(spots == '1')
{
diceA.addSnakeEyes();
}
else if(spots == '2')
{
diceA.addTwos();
}
else if(spots == '3')
{
diceA.addThrees();
}
else if(spots == '4')
{
diceA.addFours();
}
else if(spots == '5')
{
diceA.addFives();
}
else if(spots == '6')
{
diceA.addSixes();
}
return diceA;
}
}
DICE SIMULATION DRIVER CLASS
public class DiceSimulationDriver
{
/**
* @param args
*/
public static void main(String[] args)
{
//Creating a Dice Simulator object
DiceSimulator simulator = new DiceSimulator();
//Number of rolls
int numRolls = 10000;
DiceAccumulator accumulator = simulator.runSimulation(numRolls);
System.out.println("Number of rolls: " + numRolls);
System.out.println("Number snake eyes: " + accumulator.getSnakeEyes());
System.out.println("Number twos: " + accumulator.getTwos());
System.out.println("Number threes: " + accumulator.getThrees());
System.out.println("Number fours: " + accumulator.getFours());
System.out.println("Number fives: " + accumulator.getFives());
System.out.println("Number sixes: " + accumulator.getSixes());
}
}
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