Why my Program is showing this type of Error while iterating ArrayList using foreach loop?

Question

[I cannot be cast to java.lang.Integer at com.cg.genuine.ui.ArrayLisPr.main(ArrayLisPr.java:12)

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

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

        int[] x={11,20,3,4,5};
        List<Integer> po = new ArrayList(Arrays.asList(x));
        for(Integer val:po){
            System.out.println(val);
        }
    }
}

Mureinik · Accepted Answer · 2020-03-14 14:08:38Z

1

x is a single object, which is an int[], and as such, can't be cast to an Integer. If you remove the intermediate variable and use Arrays.asList directly, Java will be able to autobox each int to an Integer individually:

List<Integer> po = new ArrayList<>(Arrays.asList(11,20,3,4,5));

EDIT:

If you want to keep the int[] reference, you'll have to convert it to a List<Integer> manually. One way to do so is to stream it and box all the elements:

List<Integer> po = Arrays.stream(x).boxed().collect(Collectors.toList());

edited Mar 14, 2020 at 14:08

answered Mar 14, 2020 at 14:04

Mureinik

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3 Comments

Ritu Raj Shrivastava Over a year ago

What if I want to convert Integer Array to ArrayList using its Array Object reference?

Mureinik Over a year ago

@RituRajShrivastava you'll have to convert it yourself. See my edited answer for the details.

Naman Over a year ago

List<Integer> po = new ArrayList<>(Arrays.asList(11,20,3,4,5)) could be simplified to List<Integer> po = Arrays.asList(11,20,3,4,5)

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