我想将 Vararg Integer 转换为 Vararg int？

Question

以下代码在我的可变参数方法中使用整数值可以正常工作。但我想使用“int”而不是“Integer”。

代码如下：

package JavaPracticeShuffler;

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


public class MediumLevelExcercisesA {
    
    Scanner number;
    Scanner yorn;
    
    public MediumLevelExcercisesA(){
        
    }
    
    static void DisplayNumbers(Integer...a) {
        for (int b = 0; b < a.length; b++) {
            System.out.print(a[b]);
            System.out.print(" ");
        }
    }
    
    static void SumOfNumbers(Integer...a) {
        int total = 0;
        for (int b = 0; b < a.length; b++) {
            total += a[b];
        }
        System.out.println(" ");
        System.out.println("Sum: " + total);
    }
    
    
        
    public static void main(String[] args) {
        MediumLevelExcercisesA obj01 = new MediumLevelExcercisesA();
        List<Integer> lnumber = new ArrayList<Integer>();
                
        boolean numbercounter = true;
        
        while (numbercounter) {
            obj01.number = new Scanner(System.in);
            System.out.println("Please input a number");
            int inputnumber = obj01.number.nextInt();
            lnumber.add(inputnumber);
            
            System.out.println("Number/s you've entered so far are the following: " + lnumber);
            
            obj01.yorn = new Scanner(System.in);
            System.out.println("Do you want to continue?");
            String iyorn = obj01.yorn.nextLine().toUpperCase();
            
            if (iyorn.equals("YES")||iyorn.equals("Y")) {
                System.out.println("You've answered yes, program will proceed.");
            }
            else if (iyorn.equals("NO")||iyorn.equals("N")) {
                System.out.println("You've answered no, program ends.");
                numbercounter = false;
                break;
            }
            else {
                System.out.println("Answer not understood, program continues.");
            }
        } //end of while loop.
        
        System.out.println("Final review of numbers entered: " + lnumber);
        
        Integer[] intarray = new Integer[lnumber.size()];
        intarray = lnumber.toArray(intarray);
        MediumLevelExcercisesA.DisplayNumbers(intarray);
        MediumLevelExcercisesA.SumOfNumbers(intarray);
    }
    
}

我想在我的方法中使用“int....variable”而不是“Integer...variable”。我假设我需要将变量“intarray”转换为 int。

请帮我解决这个问题，谢谢。

Answer 1

您可以使用带有自动装箱功能的for 循环从您的列表中创建一个int 数组。然后你就可以改变所有的方法签名了。

int[] intarray = new int[lnumber.size()];
for(int i = 0; i < intarray.length; i++)
     intarray[i] = lnumber.get(i);

您也可以使用 Streams。

int[] intarray = lnumber.stream().mapToInt(Integer::intValue).toArray();

Answer 2

您需要执行以下步骤将程序从 Integer 更改为 int...

1. 将DisplayNumbers(Integer...a)的参数改为DisplayNumbers(int...a)

2. 再次将SumOfNumbers(Integer...a)的参数更改为SumOfNumbers(int...a)

3. 之后，您需要在main 方法中进行一些代码更改。即代替

   Integer[] intarray = new Integer[lnumber.size()];
   intarray = lnumber.toArray(intarray);
   

你需要写

int[] intarray = lnumber.stream().mapToInt(i -> i).toArray();

请找到完整的程序：

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


public class MediumLevelExcercisesA {

Scanner number;
Scanner yorn;

public MediumLevelExcercisesA(){

}

static void DisplayNumbers(int[] a) {
    for (int b = 0; b < a.length; b++) {
        System.out.print(a[b]);
        System.out.print(" ");
    }
}

static void SumOfNumbers(int...a) {
    int total = 0;
    for (int b = 0; b < a.length; b++) {
        total += a[b];
    }
    System.out.println(" ");
    System.out.println("Sum: " + total);
}



public static void main(String[] args) {
    MediumLevelExcercisesA obj01 = new MediumLevelExcercisesA();
    List<Integer> lnumber = new ArrayList<Integer>();

    boolean numbercounter = true;

    while (numbercounter) {
        obj01.number = new Scanner(System.in);
        System.out.println("Please input a number");
        int inputnumber = obj01.number.nextInt();
        lnumber.add(inputnumber);

        System.out.println("Number/s you've entered so far are the following: " + lnumber);

        obj01.yorn = new Scanner(System.in);
        System.out.println("Do you want to continue?");
        String iyorn = obj01.yorn.nextLine().toUpperCase();

        if (iyorn.equals("YES")||iyorn.equals("Y")) {
            System.out.println("You've answered yes, program will proceed.");
        }
        else if (iyorn.equals("NO")||iyorn.equals("N")) {
            System.out.println("You've answered no, program ends.");
            numbercounter = false;
            break;
        }
        else {
            System.out.println("Answer not understood, program continues.");
        }
    } //end of while loop.

    System.out.println("Final review of numbers entered: " + lnumber);

    //Remove below two commented line because it is not need further
    //Integer[] intarray = new Integer[lnumber.size()];
    //intarray = lnumber.toArray(intarray);
    // This can be used for if not java 8 compatible
    /*int[] intarray = new int[lnumber.size()];
    Integer[] temp = lnumber.toArray(new Integer[lnumber.size()]);
    for (int n = 0; n < lnumber.size(); ++n) {
        intarray[n] = temp[n];
    }*/
    //Java 8 and above
    int[] intarray = lnumber.stream().mapToInt(i -> i).toArray();

    MediumLevelExcercisesA.DisplayNumbers(intarray);
    MediumLevelExcercisesA.SumOfNumbers(intarray);
}

}