Infinite Loop? How??

Question about the task

Under discussion

Greetings friends, this exercise is driving me crazy on several accounts, but I'll just highlight one. The compiler claims I have an infinite loop in my while() statement. How is this the case? I have a list of set length. The code is written correctly as far as I can tell. Anyone see anything that I am not seeing? : / Mike

Use the keyboard to enter 2 numbers N and M.
Enter N strings and put them in a list.
Move the first M strings to the end of the list.
Display the list, each value on a new line.

Note:

all numbers and strings must be entered from the keyboard with a new line;
you must not create more than one list.

Requirements:

Declare a string list variable and immediately initialize it.
Read numbers N and M from the keyboard. Read N strings and add them to the list.
Move the first M strings to the end of the list.
Display the list, each value on a new line.

package en.codegym.task.jdk13.task07.task0720; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.Iterator; /* Shuffled just in time */ public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String nString = reader.readLine(); Integer n = Integer.parseInt(nString); String mString = reader.readLine(); Integer m = Integer.parseInt(mString); //write your code here ArrayList<String> list = new ArrayList<String>(); for(int i = 0; i < n; i++){ String s = reader.readLine(); list.add(s); } ArrayList<String> subList = new ArrayList<String>(list.subList(0, m)); list.addAll(subList); Iterator<String> stringIterator = list.iterator(); while(stringIterator.hasNext()){ /* if(stringIterator.nextIndex() < 4){ stringIterator.remove(); }*/ } for(String element : list){ System.out.println(element); } } }

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P.B.Kalyan Krishna

Level 24 , Guntur, India

1 April 2022, 05:54

Yes. It is true, as far as the while loop is concerned. But you can do this problem without an Iterator and a while loop. Check this out. for(int i = 0; i < N; i++) { list.add(reader.readLine()); } for(int i = 0; i < M; i++) { String str = list.get(0); list.remove(0); list.add(str); } Hope this helps!

Guadalupe Gagnon

Level 37 , Tampa, United States

31 March 2022, 20:22

while(stringIterator.hasNext()){
   /* if(stringIterator.nextIndex() < 4){
         stringIterator.remove();
   }*/
}

This code is an infinite loop. The hasNext() method or the Iterator class returns true when there are still undread items the collection that the Iterator was created from. The way that it moves through the list is when the next() method is called. Without the next() method being called then the items in the list are not read and the hasNext() method will always return true. In a loop this creates an infinite.