Codes in the current thread execute first before the codes in Thread.run()

[Karl San Gabriel]

Hello there!

This is not my first time visiting this helpful site. Today I have decided to participate.
I have a question though. I have the following code:

public class TestClass {
    private static void fun(final int i) {
        new Thread(new Runnable() {
            public void run() {System.out.println(i);}
         }).start(); 
    }
    public static void main(String[] args) {
        System.out.println(1);
        fun (2);
        System.out.println(3);
        fun (4);
        System.out.println(5);
    }
}

Executing this code always displays lines 1, 3, and 5 first before showing the other values.
I do not know what explanation is for this behavior and I couldn't find anything about this on the Internet.

I'd love to hear your thoughts about this.

[Christophe Verré]

I don't think that you can predict which one will go first. You may have different results, depending on the load on your machine for example.

[Karl San Gabriel]

Christophe Verré wrote:I don't think that you can predict which one will go first. You may have different results, depending on the load on your machine for example.

Hi Christophe,

I think you are right. That is also my expectation about the Threads. I modified the codes a bit to put in some "load" before the execution of println()'s in the current thread.

    
    public static void main(String[] args) throws Exception {
        fun (2);
   	fun (4);
   	fun (7);
   	fun (6);

   	 for(int i =0 ; i<10000; i++) {
   	    	StringBuffer sb = new StringBuffer();
   	    	sb.append("Run the other Threads first, please.");
   	    	sb.append("Run the other Threads first, please.");
   	    	sb.append("Run the other Threads first, please.");
   	    	// Just a "load" to delay the execution of println()'s below
   	}

   	System.out.println(1);
        System.out.println(3);       
        System.out.println(5);
    }

Thank you for the help.

Karl

[Richa Khan]

Hey for the same program on running several times, I am getting only these 3 solutions. Why so?

1
3
5
4
2

1
3
5
2
4

1
3
2
5
4

Thanks.

[Wouter Oet]

Apparently your machine likes it that way You can't predict the ordering. Maybe it's because of the JVM you're using, or your cpu, or the load of the cpu. You can't say. I'm getting different results.