Question

我写了一个程序来打印出所有素数达到极限。然后将这些素数放入ArrayList，将此ArrayList转换为数组，最后用它们的索引打印出数字。

注意：我无法打印带有for循环的ArrayList，只能使用数组，因此转换。

我的问题是：

无论如何都要在没有先将数字推入ArrayList的情况下进行，而是将它们立即放入长度为＆lt;的数组中。限制。

谢谢你的帮助！在过去的两天里一直在浏览SO而且找不到任何东西

import java.util.Scanner;
import java.util.ArrayList;

public class test {
public static void main(String[] args){

    //get input till which prime number to be printed
    System.out.print("Enter the number till which prime number to be printed: ");

    int limit = new Scanner(System.in).nextInt();

    System.out.print("\n");

    ArrayList<Integer> myArray = new ArrayList<Integer>();



    //printing primer numbers till the limit ( 1 to 10)
    System.out.println("Printing prime number from 1 to " + limit + "\n");

    for(int number=2; number <= limit; number++){
        if(isPrime.numberPrime(number)){
            myArray.add(number);    
        }   
    }

    System.out.println(myArray + "\n");


    //Convert ArrayList into an Array
    int[] newArray = new int[myArray.size()];

    for(int i = 0; i < myArray.size(); i++) {

            newArray[i] = myArray.get(i);

    }
    System.out.println("There were " + myArray.size() + " prime numbers");
    System.out.println("Index\tValue");

    for(int counter = 0; counter<newArray.length; counter++){
        System.out.println(counter+1 + "\t" + newArray[counter]);
    }

}

结果如下：输入要打印的素数的数字：10

Printing prime number from 1 to 10

[2, 3, 5, 7]

There were 4 prime numbers
Index   Value
1   2
2   3
3   5
4   7

Answer 1

无需这样做

//Convert ArrayList into an Array
int[] newArray = new int[myArray.size()];

for(int i = 0; i < myArray.size(); i++) {

        newArray[i] = myArray.get(i);

}
System.out.println("There were " + myArray.size() + " prime numbers");
System.out.println("Index\tValue");

for(int counter = 0; counter<newArray.length; counter++){
    System.out.println(counter+1 + "\t" + newArray[counter]);
}

代替这一点，只需写下

即可

System.out.println("There were " + myArray.size() + " prime numbers");
System.out.println("Index\tValue");
for(int i=0;i<myArray.size();i++)
System.out.println(i+1 + "\t" + myArray.get(i));

在emty数组java

1 个答案: