Java 如何使用类 Math 用从 0 到 99 的随机数填充数组？
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How to fill an array with random numbers from 0 to 99 using the class Math?
提问by Yakov Stoykov
I wrote the code, but there is no conversion from double to int.
我写了代码，但是没有从double到int的转换。
public class Array {
public static void main(String[] args) {
int i;
int[] ar1 = new int[100];
for(int i = 0; i < ar1.length; i++) {
ar1[i] = int(Math.random() * 100);
System.out.print(ar1[i] + " ");
}
}
}
How can it be corrected?
如何纠正？
采纳答案by Thusitha Thilina Dayaratne
It should be like
它应该像
ar1[i] = (int)(Math.random() * 100);
When you cast, cast type should be in brackets e.g. (cast type)value
转换时，转换类型应在括号中，例如 (cast type)value
回答by talex
ar1[i] = (int)(Math.random() * 100);
Conversion in Java looks like cast in C.
Java 中的转换看起来像 C 中的强制转换。
回答by Grim
Try this:
尝试这个：
package studing;
public class Array {
public static void main(String[] args) {
Random r = new Random();
int[] ar1 = new int[100];
for(int i = 0; i < ar1.length; i++) {
ar1[i] = r.nextInt(100);
System.out.print(ar1[i] + " ");
}
}
}
Why?
为什么？
- Using
Math.random()can return 1, this meansMath.random()*100can return 100, but OP asked for maximum 99! UsingnextInt(100)is exclusive 100, it can only return values from 0 to 99. Math.random()can not return-0.000001that would be round to0and1.0000001can not be returned that should round to1. So you have less chance to get0or99than all the numbers between. This way it is not realy random, to guess "its not0or99" is more true than "its not1or98".- Also it do not make a detour via casting and mathematic operations you don't realy need, hey you dont need to
strictfpon amd-cpus or old intel-cpus.
- 使用
Math.random()can return 1，这意味着Math.random()*100可以返回 100，但是 OP 要求最大 99！使用nextInt(100)是独占 100，它只能返回 0 到 99 之间的值。 Math.random()不能返回-0.000001将舍入到0并且1.0000001不能返回到应舍入到1。因此，您获得0或99之间的所有数字的机会都较小。这样它就不是真正随机的，猜测“它不是0或99”比“它不是1或98”更真实。- 此外，它不会通过您并不真正需要的转换和数学运算绕道而行，嘿，您不需要
strictfp在 amd-cpus 或旧的 intel-cpus 上。
回答by user1932890
This is not actually using the java.lang.Mathclass, but in Java 8 a random array can also be created in this fashion:
这实际上并未使用java.lang.Math该类，但在 Java 8 中也可以以这种方式创建随机数组：
int[] random = new Random().ints(100, 0, 100).toArray();
int[] random = new Random().ints(100, 0, 100).toArray();
回答by user3743369
My solution uses Random class instead of Math.random. Here it is.
我的解决方案使用 Random 类而不是 Math.random。这里是。
private static int[] generateArray(int min, int max) { // generate a random size array with random numbers
Random rd = new Random(); // random class will be used
int randomSize = min + rd.nextInt(max); // first decide the array size (randomly, of course)
System.out.println("Random array size: " + randomSize);
int[] array = new int[randomSize]; // create an array of that size
for (int i = 0; i < randomSize; i++) { // iterate over the created array
array[i] = min + rd.nextInt(max); // fill the cells randomly
}
return array;
}
