Design choice between ArrayList and LinkedList

Question

Can someone clarify me which is better suited (efficient) for use?
It appears to me that both can be used very much interchangeably at least from functionality point of view. :(

Answer 1

Using the following code (and I'm sure someone will come nitpicking about it) I get the (expected, at least by me from prior experience) result that iteration over a LinkedList is about twice as fast as iteration over an ArrayList, but lookup operations on an ArrayList are substantially faster:
package jtw.test;
import java.util.*;
public class SpeedTest {
    public static void main(String... args) throws Exception {
        List<Integer> linked = new LinkedList<Integer>();
        List<Integer> arr = new ArrayList<Integer>();
        for (int i = 0; i < 1e3; i++) {
            linked.add(i);
            arr.add(i);
        long r = 0;
        Date startLinked = new Date();
        for (int i = 0; i < 1e3; i++) {
            for (Integer q: linked) {
                 r += q;
        Date stopLinked = new Date();
        System.out.println("Total: " + r);
        r = 0;
        Date startArr = new Date();
        for (int i = 0; i < 1e3; i++) {
            for (Integer q: arr) {
                 r += q;
        Date stopArr = new Date();
        System.out.println("Total: " + r);
        System.out.println("LinkedList iteration: " + startLinked + " to " + stopLinked + " took " + (stopLinked.getTime() - startLinked.getTime()));
        System.out.println(" ArrayList iteration: " + startArr + " to " + stopArr + " took " + (stopArr.getTime() - startArr.getTime()));
         r = 0;
        startLinked = new Date();
        for (int i = 0; i < 1e3; i++) {
            for (int j = 999; j >= 0; j--) {
                 r += linked.get(j);
        stopLinked = new Date();
        System.out.println("Total: " + r);
        r = 0;
        startArr = new Date();
        for (int i = 0; i < 1e3; i++) {
            for (int j = 999; j >= 0; j--) {
                 r += arr.get(j);
        stopArr = new Date();
        System.out.println("Total: " + r);
        System.out.println("LinkedList lookup: " + startLinked + " to " + stopLinked + " took " + (stopLinked.getTime() - startLinked.getTime()));
        System.out.println(" ArrayList lookup: " + startArr + " to " + stopArr + " took " + (stopArr.getTime() - startArr.getTime()));
}Gets the result:
D:\jdk1.6.0_05\bin\java -Didea.launcher.port=7540 "-Didea.launcher.bin.path=C:\Program Files\JetBrains\IntelliJ IDEA 8.0.1\bin" -Dfile.encoding=windows-1252 -classpath "D:\jdk1.6.0_05\jre\lib\charsets.jar;D:\jdk1.6.0_05\jre\lib\deploy.jar;D:\jdk1.6.0_05\jre\lib\javaws.jar;D:\jdk1.6.0_05\jre\lib\jce.jar;D:\jdk1.6.0_05\jre\lib\jsse.jar;D:\jdk1.6.0_05\jre\lib\management-agent.jar;D:\jdk1.6.0_05\jre\lib\plugin.jar;D:\jdk1.6.0_05\jre\lib\resources.jar;D:\jdk1.6.0_05\jre\lib\rt.jar;D:\jdk1.6.0_05\jre\lib\ext\dnsns.jar;D:\jdk1.6.0_05\jre\lib\ext\localedata.jar;D:\jdk1.6.0_05\jre\lib\ext\sunjce_provider.jar;D:\jdk1.6.0_05\jre\lib\ext\sunmscapi.jar;D:\jdk1.6.0_05\jre\lib\ext\sunpkcs11.jar;F:\dev\Euler\out\production\Euler;C:\Program Files\JetBrains\IntelliJ IDEA 8.0.1\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain jtw.test.SpeedTest
Total: 499500000
Total: 499500000
LinkedList iteration: Wed Jan 21 07:32:41 CET 2009 to Wed Jan 21 07:32:41 CET 2009 took 30
ArrayList iteration: Wed Jan 21 07:32:41 CET 2009 to Wed Jan 21 07:32:41 CET 2009 took 53
Total: 499500000
Total: 499500000
LinkedList lookup: Wed Jan 21 07:32:41 CET 2009 to Wed Jan 21 07:32:42 CET 2009 took 424
ArrayList lookup: Wed Jan 21 07:32:42 CET 2009 to Wed Jan 21 07:32:42 CET 2009 took 22
Process finished with exit code 0Given the internal representation of the datatypes, this is to be expected.