Java 蒙特卡罗模拟
我是一名Java编程课程的学生。我的问题是关于蒙特卡罗模拟的解释。我应该找到从一个有3个25美分和3个便士的钱包中取出3个25美分或3个便士的概率。硬币一旦被拣走，就不会被替换。概率应为0.1xxxxxx。我的答案一直是0或1。这就是我目前所拥有的Java 蒙特卡罗模拟,java,simulation,probability,montecarlo,Java,Simulation,Probability,Montecarlo,我是一名Java编程课程的学生。我的问题是关于蒙特卡罗模拟的解释。我应该找到从一个有3个25美分和3个便士的钱包中取出3个25美分或3个便士的概率。硬币一旦被拣走，就不会被替换。概率应为0.1xxxxxx。我的答案一直是0或1。这就是我目前所拥有的 public class CoinPurse { public static void main(String[] args) { System.out.print("Probability of Drawing 3 coin
public class CoinPurse {
public static void main(String[] args) {
System.out.print("Probability of Drawing 3 coins of the Same Type - ");
System.out.println(coinPurseSimulation(100));
}
/**
Runs numTrials trials of a Monte Carlo simulation of drawing
3 coins out of a purse containing 3 pennies and 3 quarters.
Coins are not replaced once drawn.
@param numTrials - the number of times the method will attempt to draw 3 coins
@returns a double - the fraction of times 3 coins of the same type were drawn.
*/
public static double coinPurseSimulation(int numTrials) {
final int P = 1;
final int Q = 2;
int [] purse = {Q, Q, Q, P, P, P};
int [] drawCoins = new int[3];
for (int draw = 0; draw < 3; draw ++) {
int index = (int)(Math.random() * purse.length);
drawCoins[draw] = purse[index];
int [] newPurse = new int[purse.length-1];
int j = 0;
for (int i =0; i < purse.length; i++) {
if (i == index) {
continue;
}
newPurse[j] = purse[i];
j++;
}
purse = newPurse;
}
double number = 0.0;
double result = 0.0;
for (int i = 0; i < numTrials; i++) {
result++;
for (int j = 0; j < numTrials;j++) {
if(drawCoins[0] == drawCoins [1] && drawCoins[1] == drawCoins[2]) {
number++;
}
}
}
return number/result;
}
}
公共类{
公共静态void main（字符串[]args）{
系统输出打印（“抽取3枚相同类型硬币的概率-”；
系统输出println（coinPurseSimulation（100））；
}
/**
运行绘图的蒙特卡罗模拟的数值试验
从一个钱包里拿出3枚硬币，里面装着3个便士和3个25美分硬币。
硬币一经提取就不会被替换。
@param numTrials-该方法尝试抽取3枚硬币的次数
@返回一个双精度值-抽取3枚相同类型硬币的分数。
*/
公共静态双精度模拟（整数）{
最终INTP=1；
最终int Q=2；
int[]钱包={Q，Q，Q，P，P，P}；
整数[]抽取硬币=新整数[3]；
用于（int-draw=0；draw<3；draw++）{
int索引=（int）（Math.random（）*钱包长度）；
提取硬币[提取]=钱包[索引]；
int[]新钱包=新的int[钱包长度-1]；
int j=0；
对于（int i=0；i<1.length；i++）{
如果（i==索引）{
继续；
}
新钱包[j]=钱包[i]；
j++；
}
钱包=新钱包；
}
双倍数=0.0；
双结果=0.0；
对于（int i=0；inumTrialsnumTrials如果操作正确，答案应该是
2*（3/6）*（2/5）*（1/4）numTrialsnumTrials如果做得正确，答案应该是
2*（3/6）*（2/5）*（1/4）01numTrials*numTrialsijnumTrialspublic class CoinPurse
{
public static void main(String[] args)
{
System.out.print("Probability of Drawing 3 coins of the Same Type - ");
System.out.println(coinPurseSimulation(100));
}
/**
* Runs numTrials trials of a Monte Carlo simulation of drawing 3 coins out
* of a purse containing 3 pennies and 3 quarters. Coins are not replaced
* once drawn.
*
* @param numTrials
* - the number of times the method will attempt to draw 3 coins
* @returns a double - the fraction of times 3 coins of the same type were
* drawn.
*/
public static double coinPurseSimulation(int numTrials)
{
final int P = 1;
final int Q = 2;
double number = 0.0;
double result = 0.0;
// Changed your loop index to t to avoid conflict with i in your draw
// loop
for (int t = 0; t < numTrials; t++)
{
result++;
// Moved your draw without replacement code here
int[] purse =
{ Q, Q, Q, P, P, P };
int[] drawCoins = new int[3];
for (int draw = 0; draw < 3; draw++)
{
int index = (int) (Math.random() * purse.length);
drawCoins[draw] = purse[index];
int[] newPurse = new int[purse.length - 1];
int j = 0;
for (int i = 0; i < purse.length; i++)
{
if (i == index)
{
continue;
}
newPurse[j] = purse[i];
j++;
}
purse = newPurse;
}
// Deleted the loop with index j - you don't need to test the same
// combination numTrials times...
if (drawCoins[0] == drawCoins[1] && drawCoins[1] == drawCoins[2])
{
number++;
}
}
return number / result;
}
}
drawCoins = pickCoins(purse, 3);
Collections.shuffle（）集合maxInd private static int[] pickCoins(int[] purse, int numCoins)
{
int[] samples = new int[numCoins];
int maxInd = purse.length - 1;
for (int i = 0; i < numCoins; i++)
{
int index = (int) (Math.random() * maxInd);
int draw = purse[index];
samples[i] = draw;
// swap the already drawn sample with the one at maxInd and decrement maxInd
purse[index] = purse[maxInd];
purse[maxInd] = draw;
maxInd -= 1;
}
return samples;
}
private static int[]pickCoins（int[]钱包，int numCoins）
{
int[]样本=新的int[numCoins]；
int maxInd=钱包长度-1；
for（int i=0；i0.1xxxxxx首先，在这个简单的例子中，你可以考虑分析（或者在某种意义上<强>精确< /强>）结果。考虑程序：
2/51/4 private static int[] pickCoins(int[] purse, int numCoins)
{
int[] samples = new int[numCoins];
int maxInd = purse.length - 1;
for (int i = 0; i < numCoins; i++)
{
int index = (int) (Math.random() * maxInd);
int draw = purse[index];
samples[i] = draw;
// swap the already drawn sample with the one at maxInd and decrement maxInd
purse[index] = purse[maxInd];
purse[maxInd] = draw;
maxInd -= 1;
}
return samples;
}