ArrayList警告-警告：[unchecked]对add（E）的未经检查的调用，也不会运行文件

Question

我一直在尝试使此代码在这个阶段适合年龄。它的目的是计算一个范围内的素数，我已经编写了一种打印它们的方法。不幸的是，该代码由于警告而无法编译：

“警告：[未经检查]以未经检查的方式将add（E）作为原始类型java.util.List的成员进行调用”

-我从谷歌搜索中了解到，该警告不是为了声明您应该输入哪种类型的值，但是我已经这样做了，并且该错误似乎仅在尝试在我的.add（）函数上出现数组列表。

而当我尝试运行它时，它会给出一些更为可怕的错误，即“静态错误：未定义名称’PrimeNumbers’

我认为我在这一点上一直是代码盲的，尽管有几次尝试都无法找出我在做什么错。

import java.util.*;

public class PrimeNumbers {

    private List listOfPrimeNumbers;  //add a member variable for the ArrayList
    public static void main(String args []){    
      PrimeNumbers primeNumberList = new PrimeNumbers(50);
      primeNumberList.print();  //use our new print method
    }

public PrimeNumbers (int initialCapacity) {
    listOfPrimeNumbers = new ArrayList<Integer>(initialCapacity/2);  //initialCapacity/2 is an easy (if not tight) upper bound
    long numberOfPrimes = 0; //Initialises variable numberOfPrimes to 0
    int start = 2;
    boolean[] isPrimeNumber = new boolean[initialCapacity + 1];

    for (int i=0;i==initialCapacity;i++) {//setting all values in array of booleans to true
    isPrimeNumber[i] = true;
    }
     while (start != initialCapacity)
        {
          if (isPrimeNumber[start])
          {
            listOfPrimeNumbers.add(start);
            //add to array list
            numberOfPrimes++;
            for (int i = start; start < initialCapacity; i+=start)
            {
              isPrimeNumber[i] = false;
            }
          }
          start++;
        }
    }

 public void print()  //add this printout function
 {
     int i = 1; 
     Iterator iterator = listOfPrimeNumbers.listIterator();
     while (iterator.hasNext())
     {
          System.out.println("the " + i + "th prime is: " + iterator.next());
          i++;
     }
     //or just System.out.println(listOfPrimeNumbers);, letting ArrayList's toString do the work.  i think it will be in [a,b,c,..,z] format
 }

 public List getPrimes() {return listOfPrimeNumbers;} //a simple getter isnt a bad idea either, even though we arent using it yet
}

Answer 1

更改此行

private List listOfPrimeNumbers;  //add a member variable for the ArrayList

至

private List<Integer> listOfPrimeNumbers;  //add a member variable for the ArrayList

这将消除警告。

奖励 -您可能想在方法内部使用 增强的for循环print作为替代方法：

public void print() {
  int i = 1; 
  for (Integer nextPrime:listOfPrimeNumbers) {
      System.out.println("the " + i + "th prime is: " + nextPrime);
      i++;
  }
}