import java.util.ArrayList;
import java.util.Random;
public class ArrayDome {
static ArrayList[] a = new ArrayList[9];
static ArrayList[] b = new ArrayList[9];
public ArrayList<Integer> setRan(){
Random random = new Random();
ArrayList<Integer> list = new ArrayList<Integer>();
while(true){
int number = random.nextInt(10);
if(!list.contains(number)&&number!=0){
list.add(number);
if(list.size()==9){
break;
}
}
}
return list;
}
public static void main(String[] args) {
ArrayDome f= new ArrayDome();
a[0]= f.setRan();
b[0].add(a[0].get(0));
}
}
最后会报一个空指针的异常Exception in thread "main" java.lang.NullPointerException
at nineGame.ArrayDome.main(ArrayDome.java:25)
求教是什么原因,怎么解决呢?
import java.util.Random;
public class ArrayDome {
static ArrayList[] a = new ArrayList[9];
static ArrayList[] b = new ArrayList[9];
public ArrayList<Integer> setRan(){
Random random = new Random();
ArrayList<Integer> list = new ArrayList<Integer>();
while(true){
int number = random.nextInt(10);
if(!list.contains(number)&&number!=0){
list.add(number);
if(list.size()==9){
break;
}
}
}
return list;
}
public static void main(String[] args) {
ArrayDome f= new ArrayDome();
a[0]= f.setRan();
b[0].add(a[0].get(0));
}
}
最后会报一个空指针的异常Exception in thread "main" java.lang.NullPointerException
at nineGame.ArrayDome.main(ArrayDome.java:25)
求教是什么原因,怎么解决呢?
Test f = new Test();
a[0] = f.setRan();
b[0].add(a[0].get(0));//b[0]默认为null,可以在使用之前new一下,比如b[0]=new ArrayList();
}
static ArrayList[] b = new ArrayList[9];不知道楼主为什么会这样????
直接把数据放到ArrayList 里面不就可以了
public static void main(String[] args) {
if (args.length == 0) {
System.out.println("no args.");
}
}
}像楼主的代码层级多,又没有排版,没法看。