The second part of the tutorial series on the Java Collections Framework; in this tutorial I explain when to use LinkedList rather than ArrayList; we look at how the two classes work internally and I also explain a bit about the List interface.

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Code For This Tutorial

App.java:

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;


public class App {


	public static void main(String[] args) {
		/*
		 * ArrayLists manage arrays internally.
		 * [0][1][2][3][4][5] ....
		 */
		List<Integer> arrayList = new ArrayList<Integer>();
		
		/*
		 * LinkedLists consists of elements where each element
		 * has a reference to the previous and next element
		 * [0]->[1]->[2] ....
		 *    <-   <-
		 */
		List<Integer> linkedList = new LinkedList<Integer>();
		
		doTimings("ArrayList", arrayList);
		doTimings("LinkedList" , linkedList);
	}
	
	private static void doTimings(String type, List<Integer> list) {
		
		for(int i=0; i<1E5; i++) {
			list.add(i);
		}
		
		long start = System.currentTimeMillis();
		
		/*
		// Add items at end of list
		for(int i=0; i<1E5; i++) {
			list.add(i);
		}
		*/
		
		// Add items elsewhere in list
		for(int i=0; i<1E5; i++) {
			list.add(0, i);
		}
		
		long end = System.currentTimeMillis();
		
		System.out.println("Time taken: " + (end - start) + " ms for " + type);
	}
	


}

Time taken: 7546 ms for ArrayList
Time taken: 76 ms for LinkedList

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