Re: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Disassembling the class file shows this:
String.valueOf(null)
- INVOKESTATIC java/lang/String.valueOf:([C)Ljava/lang/String;
String.valueOf((Object)null)
- INVOKESTATIC
java/lang/String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
In the case of an ambiguous method call, the compiler chooses the most
specific one. In this case, char[] is a subclass of Object, so char[] is
chosen.
But if there is no most specific one then the compiler gives an ambiguous
method call error.
For example, compile these two classes to see the difference:
Works:
public class Null {
Null() { foobar(null); } // char[] variant most specific
static void foobar(char[] x) { }
static void foobar(Object x) { }
}
Fails:
public class Null {
Null() { foobar(null); } // compiler error
static void foobar(char[] x) { }
static void foobar(String x) { }
}
Pretty tricky...
-Archie
On Mon, Feb 2, 2009 at 12:31 AM, jan.mate...@rzf.fin-nrw.de wrote:
Very curious ...
Source of String.valueOf(Object) from JDK 1.4.2_15
/**
* Returns the string representation of the codeObject/code
argument.
*
* @param obj an codeObject/code.
* @return if the argument is codenull/code, then a string equal to
* codenull/code; otherwise, the value of
* codeobj.toString()/code is returned.
* @see java.lang.Object#toString()
*/
public static String valueOf(Object obj) {
return (obj == null) ? null : obj.toString();
}
The same for JDK 1.6.0_10
public static String valueOf(Object obj) {
return (obj == null) ? null : obj.toString();
}
But indeed:
Java 1.3.0-C : NPE
Java 1.4.2_15-b02: NPE
Java 1.5.0_12-b04: NPE
Java 1.6.0_02-b05: NPE
If I add a cast then it works
System.out.println(String.valueOf( (Object)null ));
So the compiler must bind that to another method than
String.valueOf(Object) ...
But of course, simply returning null is much easier ;)
Jan
-Ursprüngliche Nachricht-
Von: Martijn Kruithof [mailto:j...@kruithof.xs4all.nl]
Gesendet: Samstag, 31. Januar 2009 22:14
An: Ant Developers List
Betreff: Re: svn commit: r739577 -
/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Doubted it, checked it and it returned NullPointerException.
D:\type Test.java
public class Test
{
public static void main(String[] args)
{
System.out.println(String.valueOf(null));
}
}
D:\java Test
Exception in thread main java.lang.NullPointerException
at java.lang.String.init(Unknown Source)
at java.lang.String.valueOf(Unknown Source)
at Test.main(Test.java:6)
br Martijn
Matt Benson schreef:
I always thought String.valueOf(null) returned null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apach
e/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=7
39577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
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--
Archie L. Cobbs
Re: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Thanks, Archie! So String.valueOf((Object) null)
would do it. Or null. ;)
-Matt
--- Archie Cobbs archie.co...@gmail.com wrote:
Disassembling the class file shows this:
String.valueOf(null)
- INVOKESTATIC
java/lang/String.valueOf:([C)Ljava/lang/String;
String.valueOf((Object)null)
- INVOKESTATIC
java/lang/String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
In the case of an ambiguous method call, the
compiler chooses the most
specific one. In this case, char[] is a subclass of
Object, so char[] is
chosen.
But if there is no most specific one then the
compiler gives an ambiguous
method call error.
For example, compile these two classes to see the
difference:
Works:
public class Null {
Null() { foobar(null); } // char[]
variant most specific
static void foobar(char[] x) { }
static void foobar(Object x) { }
}
Fails:
public class Null {
Null() { foobar(null); } // compiler
error
static void foobar(char[] x) { }
static void foobar(String x) { }
}
Pretty tricky...
-Archie
On Mon, Feb 2, 2009 at 12:31 AM,
jan.mate...@rzf.fin-nrw.de wrote:
Very curious ...
Source of String.valueOf(Object) from JDK 1.4.2_15
/**
* Returns the string representation of the
codeObject/code
argument.
*
* @param obj an codeObject/code.
* @return if the argument is
codenull/code, then a string equal to
* codenull/code; otherwise, the
value of
* codeobj.toString()/code is
returned.
* @see java.lang.Object#toString()
*/
public static String valueOf(Object obj) {
return (obj == null) ? null :
obj.toString();
}
The same for JDK 1.6.0_10
public static String valueOf(Object obj) {
return (obj == null) ? null :
obj.toString();
}
But indeed:
Java 1.3.0-C : NPE
Java 1.4.2_15-b02: NPE
Java 1.5.0_12-b04: NPE
Java 1.6.0_02-b05: NPE
If I add a cast then it works
System.out.println(String.valueOf( (Object)null
));
So the compiler must bind that to another method
than
String.valueOf(Object) ...
But of course, simply returning null is much
easier ;)
Jan
-Ursprüngliche Nachricht-
Von: Martijn Kruithof
[mailto:j...@kruithof.xs4all.nl]
Gesendet: Samstag, 31. Januar 2009 22:14
An: Ant Developers List
Betreff: Re: svn commit: r739577 -
/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Doubted it, checked it and it returned
NullPointerException.
D:\type Test.java
public class Test
{
public static void main(String[] args)
{
System.out.println(String.valueOf(null));
}
}
D:\java Test
Exception in thread main
java.lang.NullPointerException
at java.lang.String.init(Unknown
Source)
at java.lang.String.valueOf(Unknown
Source)
at Test.main(Test.java:6)
br Martijn
Matt Benson schreef:
I always thought String.valueOf(null) returned
null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apach
e/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=7
39577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
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--
Archie L. Cobbs
Re: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
What JDK/JRE is that? The Sun Java6 API doc still
says it should return null. Whatta bitch.
-Matt
--- Martijn Kruithof j...@kruithof.xs4all.nl wrote:
Doubted it, checked it and it returned
NullPointerException.
D:\type Test.java
public class Test
{
public static void main(String[] args)
{
System.out.println(String.valueOf(null));
}
}
D:\java Test
Exception in thread main
java.lang.NullPointerException
at java.lang.String.init(Unknown Source)
at java.lang.String.valueOf(Unknown Source)
at Test.main(Test.java:6)
br Martijn
Matt Benson schreef:
I always thought String.valueOf(null) returned
null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=739577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
To unsubscribe, e-mail:
dev-unsubscr...@ant.apache.org
For additional commands, e-mail:
dev-h...@ant.apache.org
-
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AW: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Very curious ...
Source of String.valueOf(Object) from JDK 1.4.2_15
/**
* Returns the string representation of the codeObject/code argument.
*
* @param obj an codeObject/code.
* @return if the argument is codenull/code, then a string equal to
* codenull/code; otherwise, the value of
* codeobj.toString()/code is returned.
* @see java.lang.Object#toString()
*/
public static String valueOf(Object obj) {
return (obj == null) ? null : obj.toString();
}
The same for JDK 1.6.0_10
public static String valueOf(Object obj) {
return (obj == null) ? null : obj.toString();
}
But indeed:
Java 1.3.0-C : NPE
Java 1.4.2_15-b02: NPE
Java 1.5.0_12-b04: NPE
Java 1.6.0_02-b05: NPE
If I add a cast then it works
System.out.println(String.valueOf( (Object)null ));
So the compiler must bind that to another method than String.valueOf(Object) ...
But of course, simply returning null is much easier ;)
Jan
-Ursprüngliche Nachricht-
Von: Martijn Kruithof [mailto:j...@kruithof.xs4all.nl]
Gesendet: Samstag, 31. Januar 2009 22:14
An: Ant Developers List
Betreff: Re: svn commit: r739577 -
/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Doubted it, checked it and it returned NullPointerException.
D:\type Test.java
public class Test
{
public static void main(String[] args)
{
System.out.println(String.valueOf(null));
}
}
D:\java Test
Exception in thread main java.lang.NullPointerException
at java.lang.String.init(Unknown Source)
at java.lang.String.valueOf(Unknown Source)
at Test.main(Test.java:6)
br Martijn
Matt Benson schreef:
I always thought String.valueOf(null) returned null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apach
e/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=7
39577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
To unsubscribe, e-mail: dev-unsubscr...@ant.apache.org
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-
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Re: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
I always thought String.valueOf(null) returned null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=739577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
To unsubscribe, e-mail: dev-unsubscr...@ant.apache.org
For additional commands, e-mail: dev-h...@ant.apache.org
Re: svn commit: r739577 - /ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Doubted it, checked it and it returned NullPointerException.
D:\type Test.java
public class Test
{
public static void main(String[] args)
{
System.out.println(String.valueOf(null));
}
}
D:\java Test
Exception in thread main java.lang.NullPointerException
at java.lang.String.init(Unknown Source)
at java.lang.String.valueOf(Unknown Source)
at Test.main(Test.java:6)
br Martijn
Matt Benson schreef:
I always thought String.valueOf(null) returned null.
Was I on crack?
-Matt
P.S. Good to see you committing, Martijn...
--- j...@apache.org wrote:
Author: jkf
Date: Sat Jan 31 17:10:50 2009
New Revision: 739577
URL:
http://svn.apache.org/viewvc?rev=739577view=rev
Log:
Original toString would always throw a NPE.
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Modified:
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
URL:
http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java?rev=739577r1=739576r2=739577view=diff
==
---
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
(original)
+++
ant/core/trunk/src/main/org/apache/tools/ant/property/NullReturn.java
Sat Jan 31 17:10:50 2009
@@ -33,6 +33,6 @@
* {...@inheritdoc}
*/
public String toString() {
-return String.valueOf(null);
+return null;
}
}
-
To unsubscribe, e-mail: dev-unsubscr...@ant.apache.org
For additional commands, e-mail: dev-h...@ant.apache.org
-
To unsubscribe, e-mail: dev-unsubscr...@ant.apache.org
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