Getting Exception in thread “main” java.lang.NullPointerException error
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26-04-2021 - |
Pergunta
I am writing a small java code to generate random values:
import java.util.Random;
public class Rann {
static Random rand;
public static void main(String args[]){
int i;
for(i=0;i<15;i++)
System.out.println(rand.nextInt(7));
}
}
This gives an error:
Exception in thread "main" java.lang.NullPointerException
at Rann.main(Rann.java:7)
Any help would be highly appreciated. And is this the preferred way to generate random values in LeJOS?
Solução
you haven't initialized your random object
static Random rand = new Random(System.currentTimeMillis());
For best way to generate random numbers you can take a look at How do I generate random integers within a specific range in Java?
Outras dicas
You need to instantiate the Random object
Random rand = new Random();
Try this. You forgot to tell it to make a new Random-Class object.
package foso;
import java.util.Random;
public class FoSo {
static Random rand = new Random();
public static void main(String args[]){
int i;
for(i=0;i<15;i++)
System.out.println(rand.nextInt(7));
}
}
Who will initialize your rand
?
static Random rand = new Random();
You have to initialize your rand
variable before using it.
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