我一直试图让这段代码在这个阶段感觉像一个时代一样.它是为了计算一个范围内的素数,并且我已经写了一个打印它们的方法.不幸的是,代码不会编译,引用警告：
“warning：[unchecked]未选中调用add(E)作为原始类型的成员java.util.List”
– 我从谷歌搜索中了解到,这个警告是为了不声明在你的错误中应该有什么类型的值,但是我已经做到了,只有当我尝试使用.add()函数数组列表.
当我尝试运行它时,会给出一个更可怕的错误
“静态错误：未定义的名称”PrimeNumbers’
我觉得我在这一点上已经失明了,尽管有几次尝试找不到我做错了什么.有没有人可以散发一些光？非常感谢.
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
}
解决方法
改变这一行
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.
奖金 – 您可能希望在打印方法中使用增强型for循环作为替代方法：
public void print() {
int i = 1;
for (Integer nextPrime:listOfPrimeNumbers) {
System.out.println("the " + i + "th prime is: " + nextPrime);
i++;
}
}
