阵列多边形

Question

我想定义保利坤阵列，所以：

private static ArrayList<PolyDefault> basePolyList = new ArrayList<PolyDefault>(); 
//read the file and store to basePolyList 
parser.readBaseFile(filename_1, basePolyList); 
//get size of basePolyList 
int SizeOfBase = basePolyList.size(); 
//def Array of polygon  
Poly[] p4=new PolyDefault[SizeOfBase]; 
for(int i=0;i<SizeOfBase;i++) 
{ 
    p4[0].add(basePolyList.get(i)); 
    System.out.println("Poly of Base["+i+"]"+" has " +p4[i].getNumPoints()+"\n"); 
} 

，但我有这样的错误： 异常线程“main”显示java.lang.NullPointerException ... 由于任何帮助...

Answer 1

你必须初始化数组的对象：

for(int i=0;i<SizeOfBase;i++) 
{ 
    p4[i] = new Poly(); 
    p4[i].add(basePolyList.get(i)); 
    System.out.println("Poly of Base["+i+"]"+" has " +p4[i].getNumPoints()+"\n"); 
}