Question

I am trying to get used to the JavaCompiler and trying to compile programs with it, I can successfully compile programs that comprises of single file but when im trying to compile projects with multiple files. I get errors on compiling files that implement other classes and where ever the class uses a method from the implemented class.

Here is the code that I am using to compile the java code

private final String  directoryForBin = "C:/TempBINfolder/bin";

public List doCompilation(String sourceCode, String locationOfFile) {
   List<String> compile = new ArrayList<>();

    SimpleJavaFileObject fileObject = new DynamicJavaSourceCodeObject(locationOfFile, sourceCode);
    JavaFileObject javaFileObjects[] = new JavaFileObject[]{fileObject};

    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

    StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, Locale.getDefault(), null);

    Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(javaFileObjects);

    // creates a Temp BIN foler on the C: drive to add .class files for compiling      
    new File(directoryForBin).mkdirs();

    String[] compileOptions = new String[]{"-d", directoryForBin, "-classpath", System.getProperty("java.class.path")};
    Iterable<String> compilationOptions = Arrays.asList(compileOptions);

    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();

    CompilationTask compilerTask = compiler.getTask(null, stdFileManager, diagnostics, compilationOptions, null, compilationUnits);

    boolean status = compilerTask.call();

    if (!status) {//If compilation error occurs 
        // Iterate through each compilation problem and print it
        for (Diagnostic diagnostic : diagnostics.getDiagnostics()) { 
            compile.add(diagnostic.getKind().toString()+" on line  "+ diagnostic.getLineNumber() +"\nIn file:  \n"+ diagnostic.toString()+"\n\n");
        }
    }
    try {
        stdFileManager.close();//Close the file manager
    } catch (IOException e) {
        e.printStackTrace();
    }

    return compile;
}

Here is a sample of one of the classes I am trying to compile

    public class IntegerComparator 
             implements Comparator<Integer>
{
   public IntegerComparator(){}

   public int compare(Integer a, Integer b)
   {  int aValue = a.intValue();
      int bValue = b.intValue();
      return (aValue - bValue);
   }

}

Does anybody know what is going wrong here and why my code is not finding the implemented class even though it is in the same folder as that of the class implementing it?

Is it because the package is not located at the top of the program?

EDIT: This is the output error for the above example

ERROR on line  8
In file:  
/projects/Compiler/Studentfilestotest/LAB3/aroc1/a3/IntegerComparator.java:8: error: cannot find symbol
             implements Comparator<Integer>
                        ^
  symbol: class Comparator

This is what System.getProperty("java.class.path") is returning

C:\projects\Compiler\Compiler\Jar Files\jsyntaxpane-0.9.5-b29.jar;
C:\projects\Compiler\Compiler\Jar Files\jtar-1.1.jar;
C:\projects\Compiler\Compiler\Jar Files\sqlitejdbc-v056.jar;
C:\Program Files\NetBeans 7.1.2\java\modules\ext\beansbinding-1.2.1.jar;
C:\Program Files\NetBeans 7.1.2\java\modules\ext\AbsoluteLayout.jar;
C:\projects\Compiler\Compiler\Jar Files\junit-4.11-SNAPSHOT-20120416-1530.jar;
C:\projects\Compiler\Compiler\Jar Files\commons-io-2.4-bin.zip;
C:\projects\Compiler\Compiler\Jar Files\commons-io-2.4\commons-io-2.4.jar;
C:\projects\Compiler\Compiler\Jar Files\poi-3.8\poi-3.8-20120326.jar;
C:\projects\Compiler\Compiler\Jar Files\javamail-1.4.5\mail.jar;
C:\projects\Compiler\Compiler\build\classes

Answer 1

Most likely, this has nothing to do with the compiler. My guess is that this is because of an error in the source file. Did you remember to import the appropriate classes and interfaces?

Your IntegerComparator.java file needs to contain the import:

import java.util.Comparator; // <--- Import!

public class IntegerComparator 
      implements Comparator<Integer>{

   public IntegerComparator(){}

   public int compare(Integer a, Integer b){
      int aValue = a.intValue();
      int bValue = b.intValue();
      return (aValue - bValue);
   }
}

Forgetting to import appropriate classes often results in the “cannot find symbol” error messages.