I want to convert Vararg Integer to Vararg int?

Question

The below code is working fine using Integer values for my variadic method. But I want to use "int" instead of "Integer".

Here is the code:

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);
    }
    
}

I want to use "int....variable" instead of "Integer...variable" on my methods. I am assuming that I need to convert variable "intarray" to an int.

Please help I'm stuck on that part, thanks.

score 0 · Accepted Answer · answered Jul 09 '20 at 04:55

You can create a int array from your List by utilizing a for loop with autoboxing. Then you can change all the method signatures.

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

You can also use Streams.

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

score 0 · Answer 2 · answered Jul 09 '20 at 04:59

You need to do the below steps to changes your program to from Integer to int...

Change parameter of DisplayNumbers(Integer...a) to DisplayNumbers(int...a)
Again change parameter of SumOfNumbers(Integer...a) to SumOfNumbers(int...a)

After that, you need to do some code changes in the main method. i.e. instead of

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

you need to write

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

Please find the complete program:

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);
}

}

I want to convert Vararg Integer to Vararg int?

2 Answers2