CODEWITHSUNDEEP
java
user14267810
user14267810

Reputation:

How do I increment every element in an array list by n elements?

I am only editing the bottom methods for this assignment. I am trying to increase every element of the list by n or "value" elements but I can't seem to figure out how. This is my approach so far. There is a method for finding the min not shown that works as intended. I am only trying to modify the body of the second method

public class ArrayListLab 
{
   
   public static void main(String[] args) 
   {          
      ArrayList<Integer> list = new ArrayList<Integer>();
      list.add(12);
      list.add(45);
      list.add(23);
      list.add(48);  
      list.add(11);      
      System.out.println("Original list is " + list);
      System.out.println("The smallest value is " + minimum(list));   // Expected: 11
      modifyList(list, 5);
      System.out.println("The new list is " + list); 
   }
  

   public static void modifyList(List<Integer> list, int value)
   {
      for(int i = 0; i < value; i++);  
         list.get(i) += value;

   }

Upvotes: 1

Views: 3022

Answers (4)

Luke
Luke

Reputation: 154

So you have a couple of problems, first in the method modifyList() the parameter List<Integer> should actually be ArrayList<Integer>. Furthermore, your for loop must have a { instead of ; at the end of the line.

An easier way to loop through ArrayLists is

for(Integer i : list) {list.set(i, i+value); }

Also, the minimum(list) is undefined.

Check out https://www.w3schools.com/java/java_arraylist.asp for help on arraylists

Upvotes: 1

VietHTran
VietHTran

Reputation: 2318

I think you need to update your for loop to go from 0 to the length of list (for(int i = 0; i < list.size(); i++)) instead of go from 1 to value (for(int i = 0; i < value; i++)). You also need to remove the ; at the end of for statement so the Java program will take the list update code below instead of looping through an empty block of code.

Regarding how to update an ArrayList object, you can use the setfunction for that (list.set(i, list.get(i) + value))

public static void modifyList(List<Integer> list, int value) {
    for(int i = 0; i < list.size(); i++) 
        list.set(i, list.get(i) + value);

}

Update: To rotate the ArrayList like you mention, you can remove and return the first element in the list using the function remove(0) and the just add it to end of the list using the add function like you did in the main function

public static void rotateList(List<Integer> list, int n) {
    for(int i = 0; i < n; i++) 
        list.add(list.remove(0));
}

Upvotes: 2

Swapnil Padaya
Swapnil Padaya

Reputation: 695

In your code there are 2 errors

  1. Logical
  2. Syntax

Syntax for(int i = 0; i < value; i++); there's a ; and cause of that your variable i wont get recognized or say it would be out of scope.

Logical: When you did list.get(i) all it does is, Gives you the value associated with that index.
You can do like int sum = list.get(i) + value what this will do it get the value from the list at index i and then add the number 5 to it.
So now your sum holds value from index i + 5 which you wanted.

Now all you gotta do it set the index at i to the sum we calculated.
When we do list.set(i, sum) it overwrites the value at that index with our sum.

public static void modifyList(ArrayList<Integer> list, int value)
       {
          for(int i = 0 ; i < value ;i++) {
           int sum = list.get(i) + value;
            list.set(i,sum);  
          }
       }

Upvotes: 1

user6808720
user6808720

Reputation:

You should iterate over the list.

    public static void modifyList(List<Integer> list, int value)
           {
              for(int i = 0; i < list.size(); i++){  
                 list.set(i, list.get(i) + value);
              }
        
           }

Upvotes: 1

Related Questions