Common Java Error Messages
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are here : home Java Glossary E words error messages ©1996-2016 Roedy Green of Canadian Mind Products error messages compile time error messages run time error messagesThe error messages that the Java compilers and runtime produce are cryptic and the true source of the error can be far from the technical problem the compiler is pointing at. java runtime error messages A compiler looks at source code from quite a different perspective that humans
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do. You gradually get to know what your compiler really means when it says baffling things like { expected. java error messages list Sometimes a single syntax error starts off an avalanche of baffling compiler error messages. As a general rule, look slightly earlier or later of where the compiler is complaining. Fix any problems
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there and recompile. Most of the time the other errors will disappear. I repeat, don’t waste time trying to figure out arcane messages. Correct what you can and recompile. Most of the time the arcane ones will mysteriously disappear. When you start using a compiler, it is a good idea to deliberately make some common errors and see what the compiler says. Then you common error messages windows can make a table to help you later when you inadvertently make that error. (That is how I created many of the entries in the tables run time error messages and compile time error messages.) When you make an error, get a baffling error message and eventually figure out what it means, make a note to yourself to help in future when that error message appears again. It also helps to have two or three compilers on tap. When you get a really baffling error message, try some other compilers. With three variants on the error message, you have extra clues what it really means. Jikes in particular offers additional insight since its error messages are quite different from Oracle’s. Conversely, if you use Jikes, Oracle’s messages can be enlightening. This tables run time error messages and compile time error messages were constructed merging error messages from several compilers including Symantec Visual Café, IBM (International Business Machines) Visual Age, IBM Jikes, JBuilder 3 and various Sun JDKs (Java Development Kits). Please submit baffling messages from your favourite compiler. I also include run-time messages. I make no attempt to keep track
to this and will issue an error message which depends on which keyword was capitalised. The compiler will issue an error message such as: Line nn: class or interface declaration expected when,
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for example, you capitalise the keyword class. Writing a string over a new line
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Sometimes you will need to write a long string. A common error is to have a new line embedded in java error codes the string. The compiler will object to this and will issue an error message such as: Line nn: ';' expected When this happens the solution is to split the string into two, making sure that http://mindprod.com/jgloss/errormessages.html neither string has a new line in it, and concatenate them with +. Thus you might replace: String s = "A very long string which just happens to go over the end of a line and causes a problem with the compiler"; with: String s = "A very long string which just happens to go over the end "+ "of a line and causes a problem with the compiler" http://www.open.ac.uk/studentweb/m874/!synterr.htm Missing brackets in a no-argument message When you use a method which has no arguments you should place brackets after the name of the method. For example, if you have declared a method carryOut with no arguments and you want to send a message corresponding to the method to the object objSend then you should code this as: objSend.carryOut() rather than: objSend.carryOut The compiler will usually emit an error message of the form: Line nn: Invalid expression statement Forgetting to import a package This one of the most common errors that inexperienced Java programmers make. If you forget to put the required import statement at the beginning of a program, then the compiler will respond with a message such as: Line nn: Class xxxx not found in type declaration Don't forget, though, that java.lang is imported automatically and, hence, does not need an import statement. Treating a static method as if it were an instance method Static methods are associated with messages sent to classes rather than objects. A common error is to send static method messages to objects. For example, in order to calculate the absolute value of an int value and place it into the int variable you should write: int result
Common Problems (and Their Solutions) Compiler Problems Common Error Messages on Microsoft Windows Systems 'javac' is not recognized as an internal or external command, operable program or batch file If you receive https://docs.oracle.com/javase/tutorial/getStarted/problems/ this error, Windows cannot find the compiler (javac). Here's one way to tell Windows where to find javac. Suppose you installed the JDK in C:\jdk1.8.0. At the prompt you would type the following http://www.dummies.com/programming/java/tackling-error-messages-in-java-programming/ command and press Enter: C:\jdk1.8.0\bin\javac HelloWorldApp.java If you choose this option, you'll have to precede your javac and java commands with C:\jdk1.8.0\bin\ each time you compile or run a program. To avoid this error messages extra typing, consult the section Updating the PATH variable in the JDK 8 installation instructions. Class names, 'HelloWorldApp', are only accepted if annotation processing is explicitly requested If you receive this error, you forgot to include the .java suffix when compiling the program. Remember, the command is javac HelloWorldApp.java not javac HelloWorldApp. Common Error Messages on UNIX Systems javac: Command not found If you receive java error messages this error, UNIX cannot find the compiler, javac. Here's one way to tell UNIX where to find javac. Suppose you installed the JDK in /usr/local/jdk1.8.0. At the prompt you would type the following command and press Return: /usr/local/jdk1.8.0/javac HelloWorldApp.java Note: If you choose this option, each time you compile or run a program, you'll have to precede your javac and java commands with /usr/local/jdk1.8.0/. To avoid this extra typing, you could add this information to your PATH variable. The steps for doing so will vary depending on which shell you are currently running. Class names, 'HelloWorldApp', are only accepted if annotation processing is explicitly requested If you receive this error, you forgot to include the .java suffix when compiling the program. Remember, the command is javac HelloWorldApp.java not javac HelloWorldApp. Syntax Errors (All Platforms) If you mistype part of a program, the compiler may issue a syntax error. The message usually displays the type of the error, the line number where the error was detected, the code on that line, and the position of the error within the code. Here's an error caused by omitting a semicolon (;) at the end of a statement: testing
WorkSocial MediaSoftwareProgrammingWeb Design & DevelopmentBusinessCareersComputers Online Courses B2B Solutions Shop for Books San Francisco, CA Brr, it´s cold outside Search Submit Learn more with dummies Enter your email to join our mailing list for FREE content right to your inbox. Easy! Your email Submit RELATED ARTICLES Tackling Error Messages in Java Programming JavaFX For Dummies Java Programming for Android Developers For Dummies Java For Dummies, 6th Edition Java For Dummies Quick Reference Load more ProgrammingJavaTackling Error Messages in Java Programming Tackling Error Messages in Java Programming Related Book Beginning Programming with Java For Dummies, 2nd Edition By Barry Burd Sometimes, error messages can strike fear into the heart of even the bravest programmer. Fortunately some helpful, calming advice is here -- advice to help you solve the problem when you see one of these messages. NoClassDefFoundError You get this error when you're trying to run your code. So first ask yourself, did you attempt to compile the code? If so, did you see any error messages when you compiled? If you saw error messages, look for things you can fix in your .java file. Try to fix these things, and then compile the .java file again. If you normally keep code in the JavaPrograms directory, make sure that you're still working in this JavaPrograms directory. (In Windows, make sure that the command prompt says JavaPrograms.) Make sure you have an appropriately named .class file in your working directory. For instance, if you're trying to run a program named MyGreatProg, look for a file named MyGreatProg.class in your working directory. Check your classpath to make sure that it contains the .class file that you need. For example, if all your Java code is in your working directory, make sure that the classpath includes a dot. NoSuchMethodError When you encounter this error message, check for the misspelling or inconsistent capitalization of a method name. Check the capitalization of main (not Main). When you issue the java command (or do whatever you normally do to run a program in your environment), does the class that you're trying to run contain its own main method? If not, then find the class with the main method and run that class instead. Cannot Resolve Symbol If you get an error message that includes cannot resolve symbol, check the spelling and capitalization of all identifiers and keywords. Then check again. If the unresolved symbol is a variable, make sure that this variable's declaration is in the right place. For instance, if the variable is declared in a