如何使用随机数量的值创建数组

Question

I need to create an array that has a random amount of values from 8 to 12, but it says my variable is incompatible. What do I have to change? Should x not be an int?

Here is the first part of the code that includes the problem:

public class Fish {

int min = 8;
int max = 12;
int x = min + (int)(Math.random() * ((max-min) + 1));

static Fish[] myFish = new Fish[x];
static int Fcount=0;
private float weight;

public Fish(float w) { weight = w;
  myFish[Fcount] = this;
  Fcount++;
}
public float getWeight( ) { return weight; } }

The second part of my code is:

public class GoFish {
public static void main(String[] args) {

  float[] myWeights;
  for (int i = 0 ; i < x ; i++){ 
     int min = 1;
     int max = 20;
     myWeights[i] = min + (int)(Math.random() * ((max-min) + 1));
  }

  for ( float w : myWeights ) { new Fish(w); }
  for ( Fish f : Fish.myFish ) { 
     System.out.println( f.getWeight() );
  } } }

Could you also explain the problem, because I would like to understand what I'm doing wrong. I also have to make the weight a random number between 1 and 20, but I can't get this type of random numbers to work.

Edit: Since we are making the x variable static, how do I use it in the other file? because I need the array values to be random.

Answer 1

x is an instance variable. You're trying to access ( javac compiler would say "reference") instance variable ( javac would say "non-static variable") from a static context ( javac would say the same thing). This won't compile because during the static Fish[] myFish = new Fish[x]; there is no any Fish instance.

You can change your code to:

static int min = 8;
static int max = 12;
static int x = min + (int)(Math.random() * ((max-min) + 1));

This will make non-static variable x static.

Here's the official explanation of static variables (officials prefer to call them class variables).