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Could some one explain why second thread taking much lesser time for same process

public class Main {

  public static void main(String[] args) {

    final String[] test = {
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};


    long s= System.currentTimeMillis();
    new Thread(() -> {
      test[0] = test[0].replaceAll("E","  11111  ");
      System.out.println(test[0]+"  is test[0] for thread 1");
    }).start();
    long e= System.currentTimeMillis();
    System.out.println(e-s + " in t1");

    long s1= System.currentTimeMillis();

    new Thread(() -> {
      test[0] = test[0].replaceAll("E","  22222  ");
      System.out.println(test[0]+"  is test[0] for thread 2");
    }).start();

    long e1= System.currentTimeMillis();



    System.out.println(e1-s1 +" in t2");

  }
}
samabcde
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Vishal Singh
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  • Don't see much different in my machine, e.g. I see `2 in t1`. `1 in t2`. – samabcde Oct 04 '22 at 08:18
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    You are not waiting for the completion of the threads, hence you’re only measuring how long it takes *to start the threads*, which boils down to how long it takes to convert a lambda expression into a `Runnable`. Which can be longer for the first lambda expression as explained in [this answer](https://stackoverflow.com/a/34642063/2711488). However, if you fix the code to wait for the completion of the actual operation, you’re still not comparing similar operations. After the first replacement operation, there are no `E`s in the string. – Holger Oct 04 '22 at 13:13
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    Recommended read [How do I write a correct micro-benchmark in Java?](https://stackoverflow.com/q/504103/2711488) – Holger Oct 04 '22 at 13:15

0 Answers0