parser.java

是一款用JAVA 编写的编译器 具有很强的编译功能

                S.nextToken();
                if (S.token() == RBRACE) break;
                elems.append(variableInitializer());
            }
        }
        accept(RBRACE);
        return toP(F.at(newpos).NewArray(t, List.<JCExpression>nil(), elems.toList()));
    }

    /** VariableInitializer = ArrayInitializer | Expression
     */
    public JCExpression variableInitializer() {
        return S.token() == LBRACE ? arrayInitializer(S.pos(), null) : expression();
    }

    /** ParExpression = "(" Expression ")"
     */
    JCExpression parExpression() {
        accept(LPAREN);
        JCExpression t = expression();
        accept(RPAREN);
        return t;
    }

    /** Block = "{" BlockStatements "}"
     */
    JCBlock block(int pos, long flags) {
        accept(LBRACE);
        List<JCStatement> stats = blockStatements();
        JCBlock t = F.at(pos).Block(flags, stats);
        while (S.token() == CASE || S.token() == DEFAULT) {
            syntaxError("orphaned", keywords.token2string(S.token()));
            switchBlockStatementGroups();
        }
        // the Block node has a field "endpos" for first char of last token, which is
        // usually but not necessarily the last char of the last token.
        t.endpos = S.pos();
        accept(RBRACE);
        return toP(t);
    }

    public JCBlock block() {
        return block(S.pos(), 0);
    }

    /** BlockStatements = { BlockStatement }
     *  BlockStatement  = LocalVariableDeclarationStatement
     *                  | ClassOrInterfaceOrEnumDeclaration
     *                  | [Ident ":"] Statement
     *  LocalVariableDeclarationStatement
     *                  = { FINAL | '@' Annotation } Type VariableDeclarators ";"
     */
    @SuppressWarnings("fallthrough")
    List<JCStatement> blockStatements() {
//todo: skip to anchor on error(?)
        int lastErrPos = -1;
        ListBuffer<JCStatement> stats = new ListBuffer<JCStatement>();
        while (true) {
            int pos = S.pos();
            switch (S.token()) {
            case RBRACE: case CASE: case DEFAULT: case EOF:
                return stats.toList();
            case LBRACE: case IF: case FOR: case WHILE: case DO: case TRY:
            case SWITCH: case SYNCHRONIZED: case RETURN: case THROW: case BREAK:
            case CONTINUE: case SEMI: case ELSE: case FINALLY: case CATCH:
                stats.append(statement());
                break;
            case MONKEYS_AT:
            case FINAL: {
                String dc = S.docComment();
                JCModifiers mods = modifiersOpt();
                if (S.token() == INTERFACE ||
                    S.token() == CLASS ||
                    allowEnums && S.token() == ENUM) {
                    stats.append(classOrInterfaceOrEnumDeclaration(mods, dc));
                } else {
                    JCExpression t = type();
                    stats.appendList(variableDeclarators(mods, t,
                                                         new ListBuffer<JCStatement>()));
                    // A "LocalVariableDeclarationStatement" subsumes the terminating semicolon
                    storeEnd(stats.elems.last(), S.endPos());
                    accept(SEMI);
                }
                break;
            }
            case ABSTRACT: case STRICTFP: {
                String dc = S.docComment();
                JCModifiers mods = modifiersOpt();
                stats.append(classOrInterfaceOrEnumDeclaration(mods, dc));
                break;
            }
            case INTERFACE:
            case CLASS:
                stats.append(classOrInterfaceOrEnumDeclaration(modifiersOpt(),
                                                               S.docComment()));
                break;
            case ENUM:
            case ASSERT:
                if (allowEnums && S.token() == ENUM) {
                    log.error(S.pos(), "local.enum");
                    stats.
                        append(classOrInterfaceOrEnumDeclaration(modifiersOpt(),
                                                                 S.docComment()));
                    break;
                } else if (allowAsserts && S.token() == ASSERT) {
                    stats.append(statement());
                    break;
                }
                /* fall through to default */
            default:
                Name name = S.name();
                JCExpression t = term(EXPR | TYPE);
                if (S.token() == COLON && t.getTag() == JCTree.IDENT) {
                    S.nextToken();
                    JCStatement stat = statement();
                    stats.append(F.at(pos).Labelled(name, stat));
                } else if ((lastmode & TYPE) != 0 &&
                           (S.token() == IDENTIFIER ||
                            S.token() == ASSERT ||
                            S.token() == ENUM)) {
                    pos = S.pos();
                    JCModifiers mods = F.at(Position.NOPOS).Modifiers(0);
                    F.at(pos);
                    stats.appendList(variableDeclarators(mods, t,
                                                         new ListBuffer<JCStatement>()));
                    // A "LocalVariableDeclarationStatement" subsumes the terminating semicolon
                    storeEnd(stats.elems.last(), S.endPos());
                    accept(SEMI);
                } else {
                    // This Exec is an "ExpressionStatement"; it subsumes the terminating semicolon
                    stats.append(to(F.at(pos).Exec(checkExprStat(t))));
                    accept(SEMI);
                }
            }

            // error recovery
            if (S.pos() == lastErrPos)
                return stats.toList();
            if (S.pos() <= errorEndPos) {
                skip(false, true, true, true);
                lastErrPos = S.pos();
            }

            // ensure no dangling /** @deprecated */ active
            S.resetDeprecatedFlag();
        }
    }

    /** Statement =
     *       Block
     *     | IF ParExpression Statement [ELSE Statement]
     *     | FOR "(" ForInitOpt ";" [Expression] ";" ForUpdateOpt ")" Statement
     *     | FOR "(" FormalParameter : Expression ")" Statement
     *     | WHILE ParExpression Statement
     *     | DO Statement WHILE ParExpression ";"
     *     | TRY Block ( Catches | [Catches] FinallyPart )
     *     | SWITCH ParExpression "{" SwitchBlockStatementGroups "}"
     *     | SYNCHRONIZED ParExpression Block
     *     | RETURN [Expression] ";"
     *     | THROW Expression ";"
     *     | BREAK [Ident] ";"
     *     | CONTINUE [Ident] ";"
     *     | ASSERT Expression [ ":" Expression ] ";"
     *     | ";"
     *     | ExpressionStatement
     *     | Ident ":" Statement
     */
    @SuppressWarnings("fallthrough")
    public JCStatement statement() {
        int pos = S.pos();
        switch (S.token()) {
        case LBRACE:
            return block();
        case IF: {
            S.nextToken();
            JCExpression cond = parExpression();
            JCStatement thenpart = statement();
            JCStatement elsepart = null;
            if (S.token() == ELSE) {
                S.nextToken();
                elsepart = statement();
            }
            return F.at(pos).If(cond, thenpart, elsepart);
        }
        case FOR: {
            S.nextToken();
            accept(LPAREN);
            List<JCStatement> inits = S.token() == SEMI ? List.<JCStatement>nil() : forInit();
            if (inits.length() == 1 &&
                inits.head.getTag() == JCTree.VARDEF &&
                ((JCVariableDecl) inits.head).init == null &&
                S.token() == COLON) {
                checkForeach();
                JCVariableDecl var = (JCVariableDecl)inits.head;
                accept(COLON);
                JCExpression expr = expression();
                accept(RPAREN);
                JCStatement body = statement();
                return F.at(pos).ForeachLoop(var, expr, body);
            } else {
                accept(SEMI);
                JCExpression cond = S.token() == SEMI ? null : expression();
                accept(SEMI);
                List<JCExpressionStatement> steps = S.token() == RPAREN ? List.<JCExpressionStatement>nil() : forUpdate();
                accept(RPAREN);
                JCStatement body = statement();
                return F.at(pos).ForLoop(inits, cond, steps, body);
            }
        }
        case WHILE: {
            S.nextToken();
            JCExpression cond = parExpression();
            JCStatement body = statement();
            return F.at(pos).WhileLoop(cond, body);
        }
        case DO: {
            S.nextToken();
            JCStatement body = statement();
            accept(WHILE);
            JCExpression cond = parExpression();
            JCDoWhileLoop t = to(F.at(pos).DoLoop(body, cond));
            accept(SEMI);
            return t;
        }
        case TRY: {
            S.nextToken();
            JCBlock body = block();
            ListBuffer<JCCatch> catchers = new ListBuffer<JCCatch>();
            JCBlock finalizer = null;
            if (S.token() == CATCH || S.token() == FINALLY) {
                while (S.token() == CATCH) catchers.append(catchClause());
                if (S.token() == FINALLY) {
                    S.nextToken();
                    finalizer = block();
                }
            } else {
                log.error(pos, "try.without.catch.or.finally");
            }
            return F.at(pos).Try(body, catchers.toList(), finalizer);
        }
        case SWITCH: {
            S.nextToken();
            JCExpression selector = parExpression();
            accept(LBRACE);
            List<JCCase> cases = switchBlockStatementGroups();
            JCSwitch t = to(F.at(pos).Switch(selector, cases));
            accept(RBRACE);
            return t;
        }
        case SYNCHRONIZED: {
            S.nextToken();
            JCExpression lock = parExpression();
            JCBlock body = block();
            return F.at(pos).Synchronized(lock, body);
        }
        case RETURN: {
            S.nextToken();
            JCExpression result = S.token() == SEMI ? null : expression();
            JCReturn t = to(F.at(pos).Return(result));
            accept(SEMI);
            return t;
        }
        case THROW: {
            S.nextToken();
            JCExpression exc = expression();
            JCThrow t = to(F.at(pos).Throw(exc));
            accept(SEMI);
            return t;
        }
        case BREAK: {
            S.nextToken();
            Name label = (S.token() == IDENTIFIER || S.token() == ASSERT || S.token() == ENUM) ? ident() : null;
            JCBreak t = to(F.at(pos).Break(label));
            accept(SEMI);
            return t;
        }
        case CONTINUE: {
            S.nextToken();
            Name label = (S.token() == IDENTIFIER || S.token() == ASSERT || S.token() == ENUM) ? ident() : null;
            JCContinue t =  to(F.at(pos).Continue(label));
            accept(SEMI);
            return t;
        }
        case SEMI:
            S.nextToken();
            return toP(F.at(pos).Skip());
        case ELSE:
            return toP(F.Exec(syntaxError("else.without.if")));
        case FINALLY:
            return toP(F.Exec(syntaxError("finally.without.try")));
        case CATCH:
            return toP(F.Exec(syntaxError("catch.without.try")));
        case ASSERT: {
            if (allowAsserts && S.token() == ASSERT) {
                S.nextToken();
                JCExpression assertion = expression();
                JCExpression message = null;
                if (S.token() == COLON) {
                    S.nextToken();
                    message = expression();
                }
                JCAssert t = to(F.at(pos).Assert(assertion, message));
                accept(SEMI);
                return t;
            }
            /* else fall through to default case */
        }
        case ENUM:
        default:
            Name name = S.name();
            JCExpression expr = expression();
            if (S.token() == COLON && expr.getTag() == JCTree.IDENT) {
                S.nextToken();
                JCStatement stat = statement();
                return F.at(pos).Labelled(name, stat);
            } else {
                // This Exec is an "ExpressionStatement"; it subsumes the terminating semicolon
                JCExpressionStatement stat = to(F.at(pos).Exec(checkExprStat(expr)));
                accept(SEMI);
                return stat;
            }
        }
    }

    /** CatchClause     = CATCH "(" FormalParameter ")" Block
     */
    JCCatch catchClause() {
        int pos = S.pos();
        accept(CATCH);
        accept(LPAREN);
        JCVariableDecl formal =
            variableDeclaratorId(optFinal(Flags.PARAMETER),
                                 qualident());
        accept(RPAREN);
        JCBlock body = block();
        return F.at(pos).Catch(formal, body);
    }

    /** SwitchBlockStatementGroups = { SwitchBlockStatementGroup }
     *  SwitchBlockStatementGroup = SwitchLabel BlockStatements
     *  SwitchLabel = CASE ConstantExpression ":" | DEFAULT ":"
     */
    List<JCCase> switchBlockStatementGroups() {
        ListBuffer<JCCase> cases = new ListBuffer<JCCase>();
        while (true) {
            int pos = S.pos();
            switch (S.token()) {
            case CASE: {
                S.nextToken();
                JCExpression pat = expression();
                accept(COLON);
                List<JCStatement> stats = blockStatements();
                JCCase c = F.at(pos).Case(pat, stats);
                if (stats.isEmpty())
                    storeEnd(c, S.prevEndPos());
                cases.append(c);
                break;
            }
            case DEFAULT: {
                S.nextToken();
                accept(COLON);
                List<JCStatement> stats = blockStatements();
                JCCase c = F.at(pos).Case(null, stats);
                if (stats.isEmpty())
                    storeEnd(c, S.prevEndPos());
                cases.append(c);