accept method of CompilationUnit

Question

I have used Standalone ASTParser to read the variable names, but it only shows the first declared variable. It is probably because of the addition of bw.close() but I can't get where else to put it. Moreover, I can't understand how accept method of CompilationUnit can print all declared variables when ASTParser constructor is called only once.

final CompilationUnit cu = (CompilationUnit) parser.createAST(null);

    cu.accept(new ASTVisitor() {

        Set names = new HashSet();
        BufferedWriter bw = new BufferedWriter(fw);
        public boolean visit(VariableDeclarationFragment node) {
            SimpleName name = node.getName();
            this.names.add(name.getIdentifier());
            try {
                bw.write("writin");
                bw.write("Declaration of '"+name+"' at line"+cu.getLineNumber(name.getStartPosition()));
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return false; // do not continue to avoid usage info
        }
    });

Answer 1

Without seeing your whole code, I can only guess...

From what you said, I believe, you are calling bw.close() somewhere during your visit method? You should change that, so the BufferedWriter is only closed (and flushed), after the visiting is finished. To do this, declare a final BufferedWriter bw variable outside of the visitor scope and then close() it in a finally block.

Here is a complete example:

public static void parse(String fileContent) {

    ASTParser parser = ASTParser.newParser(AST.JLS8);
    parser.setKind(ASTParser.K_COMPILATION_UNIT);       
    parser.setSource(fileContent.toCharArray());

    final CompilationUnit cu = (CompilationUnit) parser.createAST(null);
    final StringWriter writer = new StringWriter();
    final BufferedWriter bw = new BufferedWriter(writer);

    try{
        cu.accept(new ASTVisitor() {
            public boolean visit(VariableDeclarationFragment node) {
                SimpleName name = node.getName();
                try {
                    bw.write("writing ");
                    bw.write("Declaration of '"+name+"' at line "+cu.getLineNumber(name.getStartPosition()));
                    bw.write("\n");
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return false; // do not continue to avoid usage info
            }
        });
    } finally{
        try {
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    System.out.println(writer.getBuffer());
}

If you use the following class as (text) input,

class TestClass{
    private Object field1;
    private Object field2;
}

you should see a similar output to this:

writing Declaration of 'field1' at line 4
writing Declaration of 'field2' at line 5