class A
{ public static void main(String[] args)
{ B[] abc=new B[3];
double m;
for(int i=0;i<3;i++)
{ abc[i].x=i*i;
m=abc[i].jieChen(3);
System.out.print("abc["+i+"].x="+m);
}
}
}class B
{ double x;
public double jieChen(int n)
{ double jiechen=1;
for(int i=1;i<=n;i++)
{ jiechen=jiechen*x*i;
}
return jiechen;
}
}
执行结果:
C:\1111\guangxue>java A
Exception in thread "main" java.lang.NullPointerException
at A.main(A.java:6)为什么是这样的提示,我弄不明白?
非常感谢!!
for(int i=0;i<3;i++)
{
abc[i] = new B(); // add code here.
abc[i].x=i*i;
m=abc[i].jieChen(3);
System.out.print("abc["+i+"].x="+m);
}
Because the declaration state "B[] abc=new B[3]" doesn't assign elements in array with B instances