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Re: How are multiple Java files compiled together?

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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

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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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