public?class?Tetromino?{
Cell[]?cells;
public?Tetromino(){
cells?=?new?Cell[4];
}
}
public?class?T?extends?Tetromino{
????????Cell[]?cells;//如果在這里寫了這一句代碼，就會(huì)報(bào)NullPointerException
public?T(){
this(0,0);
}
public?T(int?a,int?b){
this.cells=new?Cell[]{new?Cell(a,b),new?Cell(a,b+1),new?Cell(a-1,b+1),new?Cell(a,b+2)};
}
}
public?class?Test?{
public?static?void?print(Tetromino?te){
Cell[]?cells=te.cells;
boolean?mark=false;
for(int?i=0;i<=19;i++){
for(int?j=0;j<=9;j++){
for(int?k=0;k<4;k++){
if((i==cells[k].row)&(j==cells[k].col)){
System.out.print("*");
mark?=true;
break;
}
else{
mark?=false;
}
}
if(mark==false){
System.out.print("-");
}
}
System.out.println();
}
}
public?static?void?main(String[]?args)?{
//?TODO?Auto-generated?method?stub
Tetromino?t?=?new?T(1,1);
print(t);
}
}上面這段代碼，如果T類中不寫Cell[]?cells;就不會(huì)報(bào)錯(cuò)，但是寫了之后，在26行如下代碼行就會(huì)提示異常，請問是什么原因呢？？在線等，謝謝。if((i==cells[k].row)&(j==cells[k].col)){
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