对象数组的2d数组

Question

我想创建一个2D数组，每个数组都填充了另一个对象。目前我得到的是:

class CustomCache{
    boolean dirty = false;
    int age  = 0;
    String addr;
    public CustomCache(boolean a, String b, int c){
    dirty = a;
        addr = b;
        age = c;
    }
}
class Setup {
    int wpb;
    CustomCache[] wpbArray = new CustomCache[wpb];
    public Setup(int a){
        wpb = a;
    }
}

---

 Setup[][] array = new Setup[numSets][numBlocks];
 for(int i=0; i<numSets; i++){
        for(int j=0; j<numBlocks; j++){
            array[i][j] = new Setup(wpb);
            for(int k=0; k<wpb; k++){
                array[i][j].wpbArray[k] = new CustomCache(false, "", 0);
            }
        }//end inner for
    }//end outer loop

我一直得到a

java.lang.ArrayIndexOutOfBoundsException: 0

表示数组为空。知道怎么修吗?

Answer 1

这就是问题所在:

class Setup {
    int wpb;
    CustomCache[] wpbArray = new CustomCache[wpb];
    public Setup(int a){
        wpb = a;
    }
}

这条线

:

CustomCache[] wpbArray = new CustomCache[wpb];

在构造函数体之前运行—当wpb仍然为0时。你想要的:

class Setup {
    int wpb;
    CustomCache[] wpbArray;
    public Setup(int a) {
        wpb = a;
        wpbArray = new CustomCache[wpb];
    }
}

(我也建议更改为更有意义的名称，并使用私有final字段，但这是另一回事。)