Why does a Java class compile differently with a blank line?

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7
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I have the following Java class

public class HelloWorld 
 public static void main(String args)

When I compile this file and run a sha256 on the resulting class file I get 9c8d09e27ea78319ddb85fcf4f8085aa7762b0ab36dc5ba5fd000dccb63960ff HelloWorld.class.

Next I modified the class and added a blank line like this:

public class HelloWorld 

 public static void main(String args)

Again I ran a sha256 on the output expecting to get the same result but instead I got 11f7ad3ad03eb9e0bb7bfa3b97bbe0f17d31194d8d92cc683cfbd7852e2d189f HelloWorld.class.

I have read on this TutorialsPoint article that:

A line containing only white space, possibly with a comment, is known as a blank line, and Java totally ignores it.

So my question is, since Java ignores blank lines why is the compiled byte code different for both programs?

Namely the difference in the classes is that an end-of-transmission (^D) character is replaced with a end-of-text character (^C)

asked 2 hours ago

KNejad

11319

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up vote
7
down vote

favorite

I have the following Java class

public class HelloWorld 
 public static void main(String args)

When I compile this file and run a sha256 on the resulting class file I get 9c8d09e27ea78319ddb85fcf4f8085aa7762b0ab36dc5ba5fd000dccb63960ff HelloWorld.class.

Next I modified the class and added a blank line like this:

public class HelloWorld 

 public static void main(String args)

Again I ran a sha256 on the output expecting to get the same result but instead I got 11f7ad3ad03eb9e0bb7bfa3b97bbe0f17d31194d8d92cc683cfbd7852e2d189f HelloWorld.class.

I have read on this TutorialsPoint article that:

A line containing only white space, possibly with a comment, is known as a blank line, and Java totally ignores it.

So my question is, since Java ignores blank lines why is the compiled byte code different for both programs?

Namely the difference in the classes is that an end-of-transmission (^D) character is replaced with a end-of-text character (^C)

asked 2 hours ago

KNejad

11319

add a commentÂ |Â

up vote
7
down vote

favorite

I have the following Java class

public class HelloWorld 
 public static void main(String args)

When I compile this file and run a sha256 on the resulting class file I get 9c8d09e27ea78319ddb85fcf4f8085aa7762b0ab36dc5ba5fd000dccb63960ff HelloWorld.class.

Next I modified the class and added a blank line like this:

public class HelloWorld 

 public static void main(String args)

Again I ran a sha256 on the output expecting to get the same result but instead I got 11f7ad3ad03eb9e0bb7bfa3b97bbe0f17d31194d8d92cc683cfbd7852e2d189f HelloWorld.class.

I have read on this TutorialsPoint article that:

A line containing only white space, possibly with a comment, is known as a blank line, and Java totally ignores it.

So my question is, since Java ignores blank lines why is the compiled byte code different for both programs?

Namely the difference in the classes is that an end-of-transmission (^D) character is replaced with a end-of-text character (^C)

asked 2 hours ago

KNejad

11319

I have the following Java class

public class HelloWorld 
 public static void main(String args)

When I compile this file and run a sha256 on the resulting class file I get 9c8d09e27ea78319ddb85fcf4f8085aa7762b0ab36dc5ba5fd000dccb63960ff HelloWorld.class.

Next I modified the class and added a blank line like this:

public class HelloWorld 

 public static void main(String args)

Again I ran a sha256 on the output expecting to get the same result but instead I got 11f7ad3ad03eb9e0bb7bfa3b97bbe0f17d31194d8d92cc683cfbd7852e2d189f HelloWorld.class.

I have read on this TutorialsPoint article that:

A line containing only white space, possibly with a comment, is known as a blank line, and Java totally ignores it.

So my question is, since Java ignores blank lines why is the compiled byte code different for both programs?

Namely the difference in the classes is that an end-of-transmission (^D) character is replaced with a end-of-text character (^C)

java compilation bytecode java-10

asked 2 hours ago

KNejad

11319

asked 2 hours ago

KNejad

11319

asked 2 hours ago

KNejad

11319

asked 2 hours ago

KNejad

11319

asked 2 hours ago

KNejad

11319

add a commentÂ |Â

2 Answers
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8
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Basically, line numbers are kept for debugging, so if you change your source code the way you did, your method starts at a different line and the compiled class reflects the difference.

answered 1 hour ago

Federico klez Culloca

13.7k113973

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up vote
1
down vote

You can see the change by using javap -v which will output verbose information. Like other already mentioned the difference will be in line numbers (LineNumberTable section):

$ javap -v HelloWorld.class > with-line.txt
$ javap -v HelloWorld.class > no-line.txt
$ diff with-line.txt no-line.txt
3c3
< MD5 checksum 435dbce605c21f84dda48de1a76e961f
---
> MD5 checksum 058baea07fb787bdd81c3fb3f9c586bc
51c51
< line 4: 0
---
> line 3: 0

answered 1 hour ago

Karol Dowbecki

9,76442541

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
8
down vote

accepted

Basically, line numbers are kept for debugging, so if you change your source code the way you did, your method starts at a different line and the compiled class reflects the difference.

answered 1 hour ago

Federico klez Culloca

13.7k113973

add a commentÂ |Â

up vote
8
down vote

accepted

Basically, line numbers are kept for debugging, so if you change your source code the way you did, your method starts at a different line and the compiled class reflects the difference.

answered 1 hour ago

Federico klez Culloca

13.7k113973

add a commentÂ |Â

up vote
8
down vote

accepted

Basically, line numbers are kept for debugging, so if you change your source code the way you did, your method starts at a different line and the compiled class reflects the difference.

answered 1 hour ago

Federico klez Culloca

13.7k113973

Basically, line numbers are kept for debugging, so if you change your source code the way you did, your method starts at a different line and the compiled class reflects the difference.

answered 1 hour ago

Federico klez Culloca

13.7k113973

answered 1 hour ago

Federico klez Culloca

13.7k113973

answered 1 hour ago

Federico klez Culloca

13.7k113973

answered 1 hour ago

Federico klez Culloca

13.7k113973

add a commentÂ |Â

up vote
1
down vote

You can see the change by using javap -v which will output verbose information. Like other already mentioned the difference will be in line numbers (LineNumberTable section):

$ javap -v HelloWorld.class > with-line.txt
$ javap -v HelloWorld.class > no-line.txt
$ diff with-line.txt no-line.txt
3c3
< MD5 checksum 435dbce605c21f84dda48de1a76e961f
---
> MD5 checksum 058baea07fb787bdd81c3fb3f9c586bc
51c51
< line 4: 0
---
> line 3: 0

answered 1 hour ago

Karol Dowbecki

9,76442541

add a commentÂ |Â

up vote
1
down vote

You can see the change by using javap -v which will output verbose information. Like other already mentioned the difference will be in line numbers (LineNumberTable section):

$ javap -v HelloWorld.class > with-line.txt
$ javap -v HelloWorld.class > no-line.txt
$ diff with-line.txt no-line.txt
3c3
< MD5 checksum 435dbce605c21f84dda48de1a76e961f
---
> MD5 checksum 058baea07fb787bdd81c3fb3f9c586bc
51c51
< line 4: 0
---
> line 3: 0

answered 1 hour ago

Karol Dowbecki

9,76442541

add a commentÂ |Â

up vote
1
down vote

You can see the change by using javap -v which will output verbose information. Like other already mentioned the difference will be in line numbers (LineNumberTable section):

$ javap -v HelloWorld.class > with-line.txt
$ javap -v HelloWorld.class > no-line.txt
$ diff with-line.txt no-line.txt
3c3
< MD5 checksum 435dbce605c21f84dda48de1a76e961f
---
> MD5 checksum 058baea07fb787bdd81c3fb3f9c586bc
51c51
< line 4: 0
---
> line 3: 0

answered 1 hour ago

Karol Dowbecki

9,76442541

You can see the change by using javap -v which will output verbose information. Like other already mentioned the difference will be in line numbers (LineNumberTable section):

$ javap -v HelloWorld.class > with-line.txt
$ javap -v HelloWorld.class > no-line.txt
$ diff with-line.txt no-line.txt
3c3
< MD5 checksum 435dbce605c21f84dda48de1a76e961f
---
> MD5 checksum 058baea07fb787bdd81c3fb3f9c586bc
51c51
< line 4: 0
---
> line 3: 0

answered 1 hour ago

Karol Dowbecki

9,76442541

answered 1 hour ago

Karol Dowbecki

9,76442541

answered 1 hour ago

Karol Dowbecki

9,76442541

answered 1 hour ago

Karol Dowbecki

9,76442541

add a commentÂ |Â

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