Week 3: Objects, files and exceptions/7. Convert to a number list

Write the method

ArrayList<Integer> numList(ArrayList<String> list)

which takes a list of strings as its parameter.
Strings containing numbers.

The method returns a new list of integer type, with the contents of the strings converted to integers.


Example method call:
public static void main(String[] parameters){
    ArrayList<String> list = new ArrayList<>();
    list.add("2");
    list.add("10");
    list.add("-999");

    System.out.println(numList(list));
}
Program outputs:
[2, 10, -999]


==========================================



import java.util.Random;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.stream.Collectors;

public class Test{
    public static void main(String[] args){
        final Random r = new Random();
        
        testaa(new int[]{4,20,3,6,7,8,9,11});
        testaa(new int[]{1,5,2,4,3,6,4,7,5,8,6,3,9,5,3});
        testaa(new int[]{-5,-4,-1,-2,-3,-6,-7});
        
        int pituus = r.nextInt(10) + 10;
        int[] l = new int[pituus];
        for (int i=0; i<pituus; i++) {
            l[i] = (100 - r.nextInt(200));
        }
        testaa(l);
        
        
    }
    
    // testaa used by main
    public static void testaa(int[] l) {
        ArrayList<String> lista = new ArrayList<>();
        
        // convert from int to string element
        for (int a : l) {
            lista.add("" + a);
        }
        System.out.println("Testing with list ");
        System.out.print("");
        tulosta(lista);

        // convert BACK from string to integer element
        System.out.println("As integers: " + numList(lista));
        System.out.println("");
    }
    
    // tulosta used by testaa
    public static void tulosta(ArrayList<String> lista) {
        System.out.print("[\"");
        // so the joined string becomes
        // [" from above
        // 1", "2", "3
        // ", " is the 'delimiter'
        // "] from below
        System.out.print(String.join("\", \"", lista));
        System.out.println("\"]");
    }
    



    // numList used by testaa
    public static ArrayList<Integer> numList(ArrayList<String> list) {
        ArrayList<Integer> list2 = new ArrayList<>();
        // convert string to integer element
        // https://www.geeksforgeeks.org/java/integer-valueof-vs-integer-parseint-with-examples/
        for (String s : list) {
            list2.add(Integer.parseInt(s));
        }
        return list2;
    }





}





Testing with list 
["4", "20", "3", "6", "7", "8", "9", "11"]
As integers: [4, 20, 3, 6, 7, 8, 9, 11]

Testing with list 
["1", "5", "2", "4", "3", "6", "4", "7", "5", "8", "6", "3", "9", "5", "3"]
As integers: [1, 5, 2, 4, 3, 6, 4, 7, 5, 8, 6, 3, 9, 5, 3]

Testing with list 
["-5", "-4", "-1", "-2", "-3", "-6", "-7"]
As integers: [-5, -4, -1, -2, -3, -6, -7]

Testing with list 
["-30", "27", "-21", "-93", "-24", "-4", "-26", "66", "82", "-14", "-60", "88", "-94", "10", "-49", "58", "-49", "-75"]
As integers: [-30, 27, -21, -93, -24, -4, -26, 66, 82, -14, -60, 88, -94, 10, -49, 58, -49, -75]