if I use a for-each loop on a linked list in java, is it guaranteed that I will iterate on the elements in the order in which they appear in the list?
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Linked list does guarantee sequential order.
Don't use linkedList.get(i), especially inside a sequential loop since it defeats the purpose of having a linked list and will be inefficient code.
Use ListIterator
ListIterator<Object> iterator = myLinkedList.listIterator();
while( iterator.hasNext()) {
System.out.println(iterator.next());
}
Each java.util.List implementation is required to preserve the order so either you are using ArrayList, LinkedList, Vector, etc. each of them are ordered collections and each of them preserve the order of insertion (see http://download.oracle.com/javase/1.4.2/docs/api/java/util/List.html)
iterate LinkedList by using iterator
LinkedList<String> linkedList = new LinkedList<String>();
linkedList.add(“Mumbai”);
linkedList.add(“Delhi”);
linkedList.add(“Noida”);
linkedList.add(“Gao”);
linkedList.add(“Patna”);
Iterator<String> itr = linkedList.iterator();
while (itr.hasNext()) {
System.out.println(“Element is =”+itr.next());
}
Reference : Java Linkedlist Examples
As the definition of Linkedlist says, it is a sequence and you are guaranteed to get the elements in order.
eg:
import java.util.LinkedList;
public class ForEachDemonstrater {
public static void main(String args[]) {
LinkedList<Character> pl = new LinkedList<Character>();
pl.add('j');
pl.add('a');
pl.add('v');
pl.add('a');
for (char s : pl)
System.out.print(s+"->");
}
}
I found 5 main ways to iterate over a Linked List in Java (including the Java 8 way):
For loop
LinkedList<String> linkedList = new LinkedList<>();
System.out.println("==> For Loop Example.");
for (int i = 0; i < linkedList.size(); i++) {
System.out.println(linkedList.get(i));
}
Enhanced for loop
for (String temp : linkedList) {
System.out.println(temp);
}
While loop
int i = 0;
while (i < linkedList.size()) {
System.out.println(linkedList.get(i));
i++;
}
Iterator
Iterator<String> iterator = linkedList.iterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
}
collection stream() util (Java 8)
linkedList.forEach((temp) -> {
System.out.println(temp);
});
One thing should be pointed out is that the running time of For Loop or While Loop is O(n square) because get(i)
operation takes O(n) time(see this for details). The other 3 ways take linear time and performs better.
Source: Stackoverflow.com