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Printing a list method return None


By : andre lemieux
Date : October 17 2020, 06:10 PM
like below fixes the issue Because the sort() method will always return None. What you should do is:
code :
list1=[1,3,4,2]
list1.sort()
print(list1)
list1=[1,3,4,2]
list2 = sorted(list1)
print(list2)


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Invoke method on every object in a list, or pass list of objects to method and return new list?


By : jakirriaaz
Date : March 29 2020, 07:55 AM
This might help you Each approach you listed would have a very low overhead. I'd go for the most readable, which IMO is with Select. To do otherwise is premature optimization.
code :
IList<NewT> newList = oldList.Select(transformer.transform).ToList();
IList<NewT> newList = new List<NewT>(oldList.Count);
for (int i = 0; i < oldList.Count; i++)
    newList[i] = transformer.transform(oldList[i]);

What to return when printing out Objects using the toString method and a for each loop?


By : Ak.kanno
Date : March 29 2020, 07:55 AM
Any of those help toString shouldn't output anything at all. Its job is to return an appropriate string representation of the relevant object, not to output that representation anywhere. That's outside its problem domain.
Instead, build and return a string (probably by using a StringBuilder).
code :
@Override
public String toString() {
    StringBuilder sb = new StringBuilder(some_appropriate_size);
    for(Object object : ArrayList) {
        sb.append("This object is a ")
          .append(object.getVariableA())
          .append(" and a ")
          .append(object.getVariableB())
          .append(".\n");
    }
    return sb.toString();
}

Multiple calls to a void method using list parameter as return value is better than a method that return a List?


By : almanmd23
Date : March 29 2020, 07:55 AM
help you fix your problem The second option MIGHT be more optimal.
The issue is the first way not only has to make another List object for every brand, which is then just thrown away but if there are a lot of cars for a brand, then Java will resize the list (which is initialized to the default size of 16) many times. The resizing operation requires copying the array. This could get expensive if you resize many times.
code :
for(Brand brand : brands) {
    addBrandOfCarsTo(result, brand));
}

How to create an Extension method for a list to return null if list is empty or return full list


By : user2026376
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Extension methods have to be in a static class and have to be static.
You could write something like:
code :
public static class EnumerableExtensions
{
    public static IList<T> GetListOrNull<T>(this IEnumerable<T> items)
    {
        if (items == null)
        {
            return null;
        }

        // optimization to avoid creating a new list when the input already implements `IList`
        if (!(items is IList<T> tmp))
        {
            tmp = items.ToList();
        }
        return tmp.Any() ? tmp : null;
    }

    // or a list-specific version
    public static IList<T> GetListOrNull<T>(this IList<T> items)
    {
        if (items == null)
        {
            return null;
        }

        return items.Any() ? items : null;
    }
}

How to return the 2 ArrayList that was stored in this method, instead of just printing it in the void?


By : Guruprasad
Date : March 29 2020, 07:55 AM
Hope this helps I just want my checkerOddEven() method to be an ArrayList type instead of void, and I want it to be able to return both Arraylist that was stored inside each variables, so that it will print out exactly like the current output with void method. , I think this is what you want?
code :
public static ArrayList<Integer>[] checkerOddEven (int[] numbers){
    ArrayList<Integer> list[]; // I create an Array of ArrayLists
    list = new ArrayList[2]; // I allocate memory for two ArrayLists inside that array. It's important to note that without this, trying to do list[0]=new ArrayList<>(); would have crashed, because there's no list[] yet.
    list[0] = new ArrayList<>();list[1] = new ArrayList<>(); //I create the ArrayList instances by calling their constructor

    for(int number : numbers){
        if(oddEven(number)){
            list[0].add(number);
        }
        else list[1].add(number);
    }

    return list;
}

public static void main(String[] args) {
    Main main = new Main();
    ArrayList<Integer>[] listOfNumbers = (checkerOddEven(main.numbers));
    System.out.print("Odds: "); for(int i=0;i<listOfNumbers[0].size();i++) System.out.print(listOfNumbers[0].get(i)+" ");
    System.out.println(); 
    System.out.print("Even: "); for(int i=0;i<listOfNumbers[1].size();i++) System.out.print(listOfNumbers[1].get(i)+" ");
}
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