as we "No keyword should be used as an Identifier in java". But there will be some words like asser or enum or any other which have been added as keyword in version 1.4, 1.5 resp. So if any older version code is used to compile with new javac, what happens if that code contains these words as an identifier?
When older code uses an identifier that is a keyword in the current version you are trying to compile the code with, you will simply get an error. The compiler won't be able to tell from the code what version it was written for.
You'll get a compile error. But you can use already compiled classes if you aren't going to make changes in your legacy code.
Thanks for your answer, After searching i got to know the answer as, if any keyword is used as an identifier then we have to compile it with its compliant compiler otherwise it gives a compiler error. So to do that say suppose if my code has a assert as an identifier which works fine with java 1.3. So i can compile it as
javac -source 1.3 example.java
which compiles fine.
Related
For whatever reason I had to change pc's as a result of the change I now have to use Java 6 (the final update) Instead of java 7. When importing my existing project to Java 6 I get the following error in my auto generated code that was generated by Netbeans and is not modifiable
cannot find symbol
symbol: variable Type
location: class Window
frame.setType(java.awt.Window.Type.POPUP); //Type is underlined
The output for the error is as follows:
javac: invalid target release: 1.7
Usage: javac <options> <source files>
use -help for a list of possible options
C:\Users\Adminstrator\Downloads\NetBeansProjects\NetBeansProjects\Pat0.3\nbproject\build-impl.xml:915: The following error occurred while executing this line:
C:\Users\Adminstrator\Downloads\NetBeansProjects\NetBeansProjects\Pat0.3\nbproject\build-impl.xml:268: Compile failed; see the compiler error output for details.
What does this do? Is it necessary, would deleting that the component help? Which component is it, is there a quick fix?
Your build.xml specifies the target="1.7" flag to javac, which java 6 doesn't know how to interpret. Changing it to 1.6 will technically get past that error.
However, the enum Window.Type was added in Java 7, so you simply can't expect changing the target to work; your project's source uses Java 7 features. I'm sure that's not the only one.
Your options are therefore to methodically go through and remove/replace all Java 7 code (likely introducing some bugs) or just to.. install Java 7.
There is somewhere in your project a setting for the java compiler that tells it to generate classes for jre7. javac from jdk6 cannot generate classes for that version, hence the error. So you should look into the properties of your project and set up javac to generate classes for jr6. You might also have fix some of your non-generated code if for example you have used features that came with java 7 such as diamond operator or multy catch block etc.
Also the javadoc for Window.Type states it is available only since 1.7. You might want to re-generate that code or better yet just install jdk7.
I'm trying to compile a whole java project dynamically using the Compiler API. My initial thoughts of achieving this is to first know how to compile it in one-line using command line, then apply the same principle/parameters on the compiler object. Problem is, I never did, err, compiled using CLI. (Disadvantage of using an IDE? Haha)
So, am I on the right track? Moreover, can the project compilation achieved in one line execution? I'm having a hard time figuring this out because of the fact that it's a project, it contains packages galore.
So you either want to learn javac or Java Compiler API?
If you want CLI compilation look at javac (Linux | windows).
Alternatively for API, then programmatic use of Java's compiler API will definitely require more that one line, this will get you the compiler:
JavaCompilercompiler =ToolProvider.getSystemJavaCompiler();
Then you'll still need to load classes, write out byte code, and possibly package as a JAR.
You should use StandardJavaFileManager as you've probably many classes to manage, there's an example in the top of the JavaCompiler javadoc, but search for StandardJavaFileManager+JavaCompiler+example to find clearer examples like this blog post.
I am currently converting from Java 1.4 to Java 1.6. When I try to recompile my code in Java 1.6 I get the following compilation error:
_getAgentInfoOperation0.setUse(com.ibm.ws.webservices.engine.enum.Use.LITERAL);
_getAgentInfoOperation0.setStyle(com.ibm.ws.webservices.engine.enum.Style.WRAPPED);
I understand that enum is a reserved word in Java 1.6. I was told that I could change the enum to enumtype and that should compile cleanly. I changed the code to enumtype:
_getAgentInfoOperation0.setUse(com.ibm.ws.webservices.engine.enumtype.Use.LITERAL);
_getAgentInfoOperation0.setStyle(com.ibm.ws.webservices.engine.enumtype.Style.WRAPPED);
When I change to enumtype I get the following two errors:
1) The method setUse(Use) in the type OperationDesc is not applicable for the arguments (Use).
2) The method setStyle(Style) in the type OperationDesc is not applicable for the arguments (Style).
Does anyone know what I need to do to get a clean compile?
Thanks,
It looks to me like OperationDesc is your code and com.ibm.ws... is a library you're using. I suspect that, even though you switched to using the new enumtype version of the library, your old code is still expecting the enum version, so it doesn't recognize the new Use or Style objects.
After reading this forum thread, I wonder if perhaps you haven't updated your build path to use com.ibm.ws.webservices.thinclient_7.0.0.jar.
Eclipse is adding #Override annotations when I implement methods of an interface. Eclipse seems to have no problem with this. And our automated build process from Cruise Control seems to have no problem with this. But when I build from the command-line, with ant running javac, I get this error:
[javac] C:\path\project\src\com\us\MyClass.java:70: method does not override a method from its superclass
[javac] #Override
[javac] ^
[javac] 1 error
Eclipse is running under Java 1.6. Cruise Control is running Java 1.5. My ant build fails regardless of which version of Java I use.
The #Override annotation spec changed in Java 1.6. In Java 1.5, the compiler did not allow the #Override annotation on implemented interface methods, but in 1.6 it does. First search result I found is a blog post here.. It was not well documented, but it did change.
Eclipse is adding it because your Eclipse is set for 1.6 compliance. You should try to keep your build and eclipse environments on the same version of Java. It's unclear to me by your specifying Cruise Control is running Java 5 on whether or not it is compiling using a separate JDK6 or not.
Separate from the above 1.5 vs 1.6 #Override annotation rules, remember that Eclipse has its own compiler implementation (not javac) and will occasionally have different behavior. Whenever something compiles in Eclipse, but not Ant or Maven, you will need to find a way to make both compilers happy.
I can't really explain the problem you're seeing but it seems to be related to the fact that JDK 5 will not allow #Override on implemented methods of an interface, only on overridden methods present in a super class.
JDK 6 will allow #Override on any of them.
If your ant build fails it may be passing a source parameter to javac, asking for JDK 5 compliance.
The direct answer to the question "Why" an error is raised by javac when #Override is used in the context of a method implementation is actually in the java specifications:
"The rationale for this is that a concrete class that implements an interface will necessarily override all the interface's methods irrespective of the #Override annotation, and so it would be confusing to have the semantics of this annotation interact with the rules for implementing interfaces."
See http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html#9.6.1.4
But apparently someone changed his mind for java 1.6 and 1.5 u21...
#Override tags for implemented methods are new to Java 1.6. In Java 1.5 #Override is only correct when overriding a method in a base class. Read more here and here.
A lot of people, including me, got busted by this. See here for a bigger SO discussion
Eclipse would be pointing to 1.6 version of Java rather than 1.5.
See here for configuring java version in eclipse.
Ensure that there is only one definition of that interface.
Example:
HttpServletRequest
This is an interface with different specs depending on provider.
Compare pax-web-jetty and apache-felix-jetty. They have different methods.
I have had the same problem when building a project with ANT. The solution to the problem was to change the following property inside the build.properties file:
javac.compiler=org.eclipse.jdt.core.JDTCompilerAdapter
to:
javac.compiler=modern
That solved the problem and the project got compiled and deployed successfully.
I'm trying to use the StringEscapeUtils.escapeXML() function from org.apache.commons.lang...
There are two versions of that function, one which expects (Writer, String) and one which just expects (String)....
http://commons.apache.org/lang/api/org/apache/commons/lang/StringEscapeUtils.html#escapeXml(java.lang.String)
I'm trying to use the version that just expects the String parameter without the Writer, but Java is complaining that I've not given it a Writer.
How do I use this in my program so that I don't need a Writer?
String escXml = StringEscapeUtils.escapeXml(attr.get());
xml = xml.concat("<"+attr.getID()+">"+escXml+"</"+attr.getID()+">");
I've also tried just doing it inline in the string itself.
xml = xml.concat("<"+attr.getID()+">"+StringEscapeUtils.escapeXml(attr.get())+"</"+attr.getID()+">");
Both of these attempts have given me the error about it expecting the Writer though. Can anyone help me with this?
Thanks,
Matt
The error message is telling you that you are passing an Object into the method, not a String.
If you are sure that the Object is a String, then you'll need to cast it to a String first.
If this doesn't work, please post the actual code that is giving you trouble.
You should compile the java class with the specify version if you have install the more than one version of java in you system.
You should compile your file using this way.
javac -target -source
E.g H:>javac -target 1.6 -source 1.6 Testt.java
So your target and Source version is tell to the java so it will call the particular version class at run time..
What exactly is the compiler error message?
is it possible that you're using a different version of the commons library that does not have the 1-parameter method?