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Re: How are multiple Java files compiled together?

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On Sunday, 27 May 2012 19:34:42 UTC-4, Knute Johnson  wrote:
> On 5/27/2012 3:48 PM, Jason Kim wrote:
> > I am new to Java.
> >
> > Here are two files.
> >
> > VolcanoApplication.java
> > class VolcanoApplication {
> > 	public static void main(String[] arguments) {
> > 		VolcanoRobot dante = new VolcanoRobot();
> > 		dante.status = "exploring";
> > 		dante.speed = 2;
> > 		dante.temperature = 510;
> > 		
> > 		dante.showAttributes();
> > 		System.out.println("Increasing speed to 3.");
> > 		dante.speed = 3;
> > 		dante.showAttributes();
> > 		System.out.println("Changing temperature to 670");
> > 		dante.temperature = 670;
> > 		dante.showAttributes();
> > 		System.out.println("Checking the temperature.");
> > 		dante.checkTemperatur();
> > 		dante.showAttributes();
> > 	}
> > }
> >
> > VolcanoRobot.java
> > class VolcanoRobot {
> > 	String status;
> > 	int speed;
> > 	float temperature;
> > 	
> > 	void checkTemperatur() {
> > 		if (temperature>  50) {
> > 			status = "returning home";
> > 			speed = 5;
> > 		}
> > 	}
> > 	
> > 	void showAttributes() {
> > 		System.out.println("Status: " + status);
> > 		System.out.println("Speed: " + speed);
> > 		System.out.println("Temperature: " + temperature);
> > 	}
> > }
> >
> > I compiled the program by doing
> > $ javac VolcanoApplication.java
> >
> > But how does Java know that VolcanoRobot.java should also be in the compilation?
> 
> If it didn't know, think about what a pain that would be every time you 
> had to compile a program with a lot of files.  You reference 
> VolcanoRobot in VolcanoApplication, the compiler looks for that that 
> class in the classpath and compiles it if necessary.
> 
> That feature can be the source of a very tricky problem and that is if 
> there is a VolcanoRobot.class file in the classpath the compiler won't 
> compile VolcanoRobot.java even if it has changed since the 
> VolcanoRobot.class file was created.
> 
> -- 
> 
> Knute Johnson

I didn't know Java compiler could be that smart.
As for the potential problem you mentioned, I don't think I'll have to worry about it any time soon. I won't be programming anything crazy complicated for some time.
Thanks Knute.

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Thread

How are multiple Java files compiled together? Jason Kim <iamjsonkim@gmail.com> - 2012-05-27 15:48 -0700
  Re: How are multiple Java files compiled together? Knute Johnson <nospam@knutejohnson.com> - 2012-05-27 16:34 -0700
    Re: How are multiple Java files compiled together? Jason Kim <iamjsonkim@gmail.com> - 2012-05-27 16:47 -0700
      Re: How are multiple Java files compiled together? Lew <noone@lewscanon.com> - 2012-05-27 20:18 -0700
        Re: How are multiple Java files compiled together? Knute Johnson <nospam@knutejohnson.com> - 2012-05-27 21:08 -0700
          Re: How are multiple Java files compiled together? Gene Wirchenko <genew@ocis.net> - 2012-05-28 09:32 -0700
            Re: How are multiple Java files compiled together? Lew <noone@lewscanon.com> - 2012-05-28 22:35 -0700
              Re: How are multiple Java files compiled together? Gene Wirchenko <genew@ocis.net> - 2012-05-29 09:20 -0700
  Re: How are multiple Java files compiled together? Roedy Green <see_website@mindprod.com.invalid> - 2012-05-27 17:35 -0700
    Re: How are multiple Java files compiled together? Roedy Green <see_website@mindprod.com.invalid> - 2012-05-27 19:34 -0700
    Re: How are multiple Java files compiled together? Roedy Green <see_website@mindprod.com.invalid> - 2012-05-28 04:00 -0700
      Re: How are multiple Java files compiled together? Lew <noone@lewscanon.com> - 2012-05-28 22:56 -0700

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