将通用ArrayList元素转换为原始类型（长整数）

Question

I would like to write a method which confronts an element of a generic ArrayList with a long number. I know that the array contains only Long values, so I don't need to check this. This is my method:

searchSum(ArrayList <T> array, long n);

The confrontation I need to do is:

array.get(index)==n

Answer 1

You cannot cast list to primitives. Java list contains Objects and the primitives are not objects. But depending on what you want to do I am pretty sure there is an easy way to achieve it. Unfortunately from your question I can hardly understand what is the goal.

If you want to find if the list contains an element you can use:

array.indexOf(new Long(n)); and it will tell you the index of the first ocurance of the element.

If you just want to see if it is there you can use array.contains(new Long(n));

If you want to sum all elements (since your method is called searchSum) you can do:

searchSum(ArrayList <T> array, long n){
for (Long element: array){
   if(Long.valueOf(n).equals(element)){
        .... do something here...
    }
  }

}