java - Arraylist IndexOutOfBounds 调试错误

Question

我收到以下错误。

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
    at java.util.ArrayList.rangeCheck(Unknown Source)
    at java.util.ArrayList.set(Unknown Source)
    at shortestPath.runQ5(shortestPath.java:181)
    at shortestPath.main(shortestPath.java:26)

给出该问题的代码如下:

 public ArrayList<Integer[]> runQ5() throws Exception   
   {        
       int oldPathCost = 0, pathCost = 0;
       ArrayList<Integer[]> temporary = new ArrayList<Integer[]>();       

       for(int i=1; i<stationNames.size(); i++)
       {
           for(int j=1; j<stationNames.size() & i != j; j++)
           {
               pathCost = runQ3(stationNames.ceilingKey(i), stationNames.ceilingKey(j));

               if(pathCost > oldPathCost)
               {
                   System.out.println(i + ", " + j + ", " +temporary.size());
                   oldPathCost = pathCost;
                   temporary.set(temporary.size(), new Integer[]{i,j});
               }
               else if(pathCost == oldPathCost)
               {
                   oldPathCost = pathCost;
                   temporary.add(new Integer[]{i,j});
               }

           }
       }

       Q6 = oldPathCost + Q6;
       return temporary;
   }

Answer 1

没有意义:

temporary.set(temporary.size(), new Integer[]{i,j});

set 用于替换列表中现有位置的值，但如果列表的当前大小为 temporary.size()，则 temporary.size()第一个索引尚未被占用。

只需写:

temporary.add(new Integer[]{i,j});

如果你想设置列表中的第temporary.size()元素。