I have just written a Java multi-threaded program in Eclipse. It compiled fine and works like a charm.
However, as this is coursework we are required to ensure that it compiles in the command line using 'javac' otherwise we score ZERO!
So, some classes compile others don't. The error I'm getting is the following ( they are all similar just with different class names, this is one example)
GateRunnable.java:7: cannot find symbol
symbol : class Station
location: class package.name.here.GateRunnable
public GateRunnable(Station st) {
^
Is this a javac issue? Any help appreciated.
Your compile -classpath and/or -sourcepath is incomplete. The compiler doesn't know where to find class Station. Here is a related question that describes how to set the classpath to include all the classes you want.
To solve the problem I was having, it was simply necessary to compile all classes by using the following command:
javac *.java
which compiles all java files in the directory.
have you compiled every .java file in your folder/packages? if not, then do so. Eclipse usually does that for you, but within the terminal it's you taking the responsibility of compiling every part of the code.
Related
I'm trying to compile java files on an EC2 instance, and am having trouble. I have several JAR files as well that are included in the classpath. The example would be a StockTrade.java (which is a stock trade object), which compiles completely without issue. In the same directory, there is the StockTradeGenerator.java, which will create StockTrade objects. When I try to compile this, it tells me it cannot find the StockTrade class (despite it being in the same directory already compiled. Specifically, there is a field within my StockTrade object that is a TradeType which is definied as an enum: BUY or SELL in the StockTrade.java code. It says it cannot find the symbol TradeType. My syntax is:
javac -cp lib/jar1.jar:lib/jar2.jar src/StockTradeGenerator.java
Does anyone know what is making it so that I cannot find TradeType when compiling StockTradeGenerator? As I said, its defined in StockTrade.java, which compiled without issue and is in the same folder/directory.
Put the current directory class path.
javac -cp .:lib/jar1.jar:lib/jar2.jar src/StockTradeGenerator.java
I was having fun coding in Java, until for some reason javac stopped compiling my code. I googled about classpath, and set my CLASSPATH to /root/java. It was not set before that.
My package is in the /.../t directory with name centralServer (i.e. /.../t/centralServer).
Now it is compiling from the /.../t directory with the command javac centralServer/TestSSData.java. (The command is called from the /.../t directory). The output it gives is
Cannot find symbol
If I run the command from /.../t/centralServer with javac TestSSData.java I get as output:
File not found.
Point me the way for any roads I can follow to fix this please?
I removed the package statement and now it compiles. However this is not the way I would like to fix it...
I'm not sure what is going wrong here. I have to write a Tetris program based off of a Skeleton given by my teacher for school. The current class that I am implmenting is called "TetrisPiece" and the abstract class being extended is called "Piece." For some reason I cannot compile my code because it cannot located the Piece class.
I have Piece.java and TetrisPiece.java in the same folder. The structure is:
/src
/TetrisPiece.java
/Piece.java
/Piece.class
I type
javac Piece.java
and it compiles correctly, then I type
javac -cp . TetrisPiece.java
and it results in a compiler error (I have to type -cp . because I messed up my classpath somehow and Java can't find the current directory). I looked through a couple similar StackOverflow Questions and they did not have an answer to this. If the information I provide is not detailed enough (which I assume it isn't) please tell me what else I should provide to give an adequate answer.
You need to compile the files at the same time:
javac Piece.java TetrisPiece.java
Then, assuming TetrisPiece has a main() method, you can run the program with:
java TetrisPiece
I am using the code from Rome's tutorials page http://wiki.java.net/twiki/bin/view/Javawsxml/Rome05TutorialFeedReader . Also trying this one: http://wiki.java.net/twiki/bin/view/Javawsxml/Rome05TutorialFeedReader
Compiling works, but I'm not sure how to run these examples. Why I just type java FeedReader or java FeedAggregator into the command line, I get the error:
C:\projects\freshmeat\src>java FeedAggregator http://freecode.com/?format=atom
Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/syndication/f
eed/synd/SyndFeed
plus the large block that follows this error
Why is this happening, how do I fix it and try these things out? How do I get something to work with Rome!?
You need to include rome in the runtime classpath (in addition to the compile-time classpath)
java -classpath lib/rome.jar FeedAggregator ...
The samples you are trying to run are in the package com.sun.syndication.samples. You say you are a complete beginner, so, to make things simpler, I would recommend that you remove the line beginning with package in each of FeedReader.java and FeedAggregator.java. Recompile the classes after removing their package directives.
Then, to run these classes, make sure you're in the same directory as the class files FeedReader.class and FeedAggregator.class that javac created. Then, try running:
java -cp c:\projects\freshmeat\libs\rome-1.0.jar;c:\projects\freshmeat\libs\jdom-1.0.jar;. FeedReader
(and similarly for FeedAggregator.)
Note also that I've added the current directory, ., to the -cp attribute. Without this, the Java virtual machine won't know that it has to look in the current directory to find your FeedReader and FeedAggregator classes.
If you were to reinstate the package directives, you'd find the class files FeedReader.class and FeedAggregator.class would be created inside a directory com\sun\syndication\samples when you compile their sources. To run the class files from this location, you'd use a command line such as
java -cp c:\projects\freshmeat\libs\rome-1.0.jar;c:\projects\freshmeat\libs\jdom-1.0.jar;. com.sun.syndication.samples.FeedReader
and you'd run this from the directory containing the com subdirectory, not the directory that contains the class files.
More information on packages in Java can be found here.
How do I create a Java package for different files? I have tried
the following. What have I done wrong? And what is the
right procedure?
The first file is:
package dil;
public class Hello
{
Support sp=new Support();
int i=sp.tin();
public void man()
{
System.out.println(i);
}
}
The second file is:
package dil;
class Support
{
public int tin()
{
return 3;
}
}
Now while I compile hello.java it shows these errors:
Hello:4:cannot find symbol
symbol: class Support
location: class dil.hello
Support sp=new Support();
^
Hello:4:cannot find symbol
symbol: class Support
location: class dil.hello
Support sp=new Support();
^
Where is the problem and how can I put both
these files in a package?
The files are in c:\src.
Assuming UNIX / Linux pathnames, a UNIX shell, etc, you need the following file structure:
/some/where/dil
/some/where/dil/hello.java
/some/where/dil/Support.java
Then set $CLASSPATH to /some/where, and compile using the commands
cd /some/where
javac dil/*.java
and run using
java dil.hello
Alternatively, you can tell java and javac what classpath to use with the -cp command line option.
You should also fix the following errors in the code:
Change the name of the "hello" class to "Hello", and rename the source file to match. Strictly speaking this is not an error, but it is a gross violation of the standard for naming Java classes.
You declare a member as "ten" but refer to it as "tin". Fix one or the other.
The entry point method in the "hello" class should be called "main" not "man", and should have a signature public static void main(String[] arg). If you don't fix these the code will compile, but the java command won't find the entry point and will fail.
Although the Support class is not public, that would not be a problem as both classes share the same package. My guess would be that you did not put both source files into a directory according to their packagename and call the javac compiler from the current directory where hello.java resides.
If a class is in package a.b this means the project structure should contain a folder ./a/b containing yourclass.java.
In your case, try to create a folder named ./dil, put your source files in it and call javac from its parent folder.
See Creating and Using Packages in Sun's Java Tutorials to learn all the details of using packages in Java.
I've spotted some things you have to check:
class hello starts with a lower case
class hello calls for sp.ten() instead of sp.tin()
Support isn't public. Make it public and try again.
I suggest you try using one of the free IDEs like Netbeans, Eclipse or IntelliJ CE. This will help you start coding rather than setting everything up the hard way.
BTW: These IDEs have quick fixes for most common problems so they not only give you the error but give you options to fix them and do it for you.