如何在java中创建和显示随机数的arraylist？
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How can I create and display an arraylist of random numbers in java?
提问by Sparky123
I'm trying to generate an arraylist of random numbers and display it. I'm not sure where I'm going wrong. I think my showArray method isn't working properly because it's displaying two random numbers and then repeating the second one n-2 times.
我正在尝试生成一个随机数数组列表并显示它。我不确定我哪里出错了。我认为我的 showArray 方法不能正常工作，因为它显示两个随机数，然后重复第二个 n-2 次。
private static ArrayList<Integer> RandomArray(int n)
{
ArrayList<Integer> arrayRandom = new ArrayList<Integer>(n);
for (int i=0; i<n; i++)
{
Random rand = new Random();
rand.setSeed(System.currentTimeMillis());
Integer r = rand.nextInt() % 256;
arrayRandom.add(r);
}
return arrayRandom;
}
private static void ShowArray(ArrayList<Integer> randomArray)
{
int n = randomArray.size();
ArrayList<Integer> showArray = new ArrayList<Integer>(n);
for (int i = 0; i<n; i++)
{
int r = randomArray.get(i);
showArray.add(r);
}
System.out.println(showArray);
}
public static void main(String args[])
{
ShowArray(RandomArray(5));
}
So for example this would produce an output of
因此，例如这将产生输出
[132, 152, 152, 152, 152]
[132, 152, 152, 152, 152]
Any help is much appreciated. Thanks in advance
任何帮助深表感谢。提前致谢
采纳答案by Jan Thom?
Take the random object out of your loop and don't set the seed everytime.
从循环中取出随机对象，不要每次都设置种子。
ArrayList<Integer> arrayRandom = new ArrayList<Integer>(n);
Random rand = new Random();
rand.setSeed(System.currentTimeMillis());
for (int i=0; i<n; i++)
{
Integer r = rand.nextInt() % 256;
arrayRandom.add(r);
}
This should work better.
这应该工作得更好。
回答by Tim Bender
You problem is that you keep resetting the seed and thus restarting the pseudo random number generator (PRNG) sequence.
您的问题是您不断重置种子，从而重新启动伪随机数生成器 (PRNG) 序列。
Do this:
做这个：
Random rand = new Random();
rand.setSeed(System.currentTimeMillis());
for (int i=0; i<n; i++)
{
Integer r = rand.nextInt(256);
arrayRandom.add(r);
}
回答by Falmarri
Don't set the seed every iteration
不要每次迭代都设置种子
Random rand = new Random();
rand.setSeed(System.currentTimeMillis());
Do it once.
做一次。
