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  1. import java.util.ArrayList;
  2.  
  3. class Ideone {
  4.  
  5.   public static final int LIST_SIZE = 1000;
  6.   public static final ArrayList<Integer> list = new ArrayList<>(LIST_SIZE);
  7.  
  8.   static {
  9.     final Integer content = Integer.valueOf(1);
  10.     for (int i = LIST_SIZE; i > 0; --i) {
  11.       list.add(content);
  12.     }
  13.   }
  14.  
  15.   static int doArrayIterator() {
  16.     int result = 0;
  17.     for (final Integer i : list) {
  18.       result += i;
  19.     }
  20.     return result;
  21.   }
  22.  
  23.   static int doArrayIndex() {
  24.     int result = 0;
  25.     for (int i = 0; i < LIST_SIZE; ++i) {
  26.       result += list.get(i);
  27.     }
  28.     return result;
  29.   }
  30.  
  31.   public static void main(String[] args) throws InterruptedException {
  32.     final int RUNS = 100000;
  33.  
  34.     int sum = 0;
  35.     for (int i = 0; i < RUNS; ++i) {
  36.       sum += doArrayIterator();
  37.       sum += doArrayIndex();
  38.     }
  39.     System.out.println("Warmup done: " + sum);
  40.  
  41.     sum = 0;
  42.     long timeStart = System.nanoTime();
  43.     for (int i = 0; i < RUNS; ++i) {
  44.       sum += doArrayIterator();
  45.     }
  46.     final long timeIterator = System.nanoTime() - timeStart;
  47.  
  48.     sum = 0;
  49.     timeStart = System.nanoTime();
  50.     for (int i = 0; i < RUNS; ++i) {
  51.       sum += doArrayIterator();
  52.     }
  53.     final long timeIndex = System.nanoTime() - timeStart;
  54.  
  55.     final double timePIterator = ((double) timeIterator) / ((double) Math.max(timeIterator, timeIndex)) * 100.0;
  56.     final double timePIndex = ((double) timeIndex) / ((double) Math.max(timeIterator, timeIndex)) * 100.0;
  57.     System.out.println(String.format("%-10s %d %10d ns %6.2f%%", "Iterator:", sum, timeIterator, timePIterator));
  58.     System.out.println(String.format("%-10s %d %10d ns %6.2f%%", "Index:", sum, timeIndex, timePIndex));
  59.   }
  60. }
  61.  
Success #stdin #stdout 3.87s 380352KB
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Standard input is empty
stdout
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Warmup done: 200000000
Iterator:  100000000 1109326391 ns  99.47%
Index:     100000000 1115199424 ns 100.00%
https://ideone.com/pAzqki
language:
Java (HotSpot 12)
created:
11 years ago
visibility:
public

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