空指针异常，第18行，请指正。
[code=Java][/code]import java.util.*;
public class Test1 {
Test1 []a;
int n;
int [] array ;
ArrayList<Integer> b = new ArrayList<Integer>();
public void initialArray(){
Scanner in = new Scanner(System.in);
n = in.nextInt();
a = new Test1[n];
array = new int [n];
for(int op = 0; op < n; op ++){
array [op] = 0;
a[op] = new Test1();
}
for(int start = 0; start < n; start ++){
for(int start1 = 0; start1 < n; start1 ++){
a[start].array[start1] =(int)((Math.random()*n)+1);
a[start].b.add(a[start].array[start1]);
}
System.out.print(a[start].b);
}
}
public void sortArray(){
for(int start = 0; start < n; start ++){
Collections.sort(a[start].b);
System.out.print(a[start].b);
}
}
public static void main(String [] args){
Test1 go = new Test1();
go.initialArray();
System.out.println();
go.sortArray();
}
}


[解决办法]

不是给你指出的错误的所在。。。我汗。。。下面代码可以了

Java code

import java.util.*;public class Test1 {    Test1[] a;    int n;    int[] array;    ArrayList<Integer> b = new ArrayList<Integer>();    public void initialArray() {        Scanner in = new Scanner(System.in);        n = in.nextInt();        a = new Test1[n];        array = new int[n];        for (int op = 0; op < n; op++) {            array[op] = 0;            Test1 t1 = new Test1();            t1.array = array;            a[op] = t1;        }        for (int start = 0; start < n; start++) {            for (int start1 = 0; start1 < n; start1++) {                a[start].array[start1] = (int) ((Math.random() * n) + 1);                a[start].b.add(a[start].array[start1]);            }            System.out.print(a[start].b);        }    }    public void sortArray() {        for (int start = 0; start < n; start++) {            Collections.sort(a[start].b);            System.out.print(a[start].b);        }    }    public static void main(String[] args) {        Test1 go = new Test1();        go.initialArray();        System.out.println();        go.sortArray();    }}
[解决办法]
Java code
a[start].array[start1] = (int) ((Math.random() * n) + 1);//a[start].array没有初始化，在你代码里面a = new Test1[n];array = new int[n];只是对当前对象的array进行了初始化，而你取得的是a[start]这里面的array都没有被初始化。所以报错