NullPointerException异常，呈锯齿状排列

Question

当我想引用数组元素的构造函数外，该程序引发我NullPointerException (location: function ratio)

private int tabPascal[][]; 


Pascal(int n){ 
    int tabPascal [][]= new int[n+1][]; 

    for(int i = 0; i <= n; i++){ 
     tabPascal[i] = new int[i+1]; 
    } 


    for(int i = 0; i < tabPascal.length; i++){ 
     for(int j = 0; j<tabPascal[i].length; j++){ 

      tabPascal[i][j] = binomial(i,j); 
      System.out.print(tabPascal[i][j] + " "); 
     } 
     System.out.println(); 
    } 

} 

...

public int ratio(int n, int k){ 

    return tabPascal[n][k]; 
} 

Answer 1

你shadowing你的实例变量你的构造函数。因此它从未初始化。

private int tabPascal[][]; 


Pascal(int n){ 
    tabPascal = new int[n+1][]; 
    .... 
}