Ant example source code file (StripJavaComments.java)

This example Ant source code file (StripJavaComments.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Ant tags/keywords

basefilterreader, chainablereader, chainablereader, io, ioexception, ioexception, reader, reader, stripjavacomments, stripjavacomments

The StripJavaComments.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.tools.ant.filters;

import java.io.IOException;
import java.io.Reader;

/**
 * This is a Java comment and string stripper reader that filters
 * those lexical tokens out for purposes of simple Java parsing.
 * (if you have more complex Java parsing needs, use a real lexer).
 * Since this class heavily relies on the single char read function,
 * you are recommended to make it work on top of a buffered reader.
 *
 */
public final class StripJavaComments
    extends BaseFilterReader
    implements ChainableReader {

    /**
     * The read-ahead character, used for effectively pushing a single
     * character back. A value of -1 indicates that no character is in the
     * buffer.
     */
    private int readAheadCh = -1;

    /**
     * Whether or not the parser is currently in the middle of a string
     * literal.
     */
    private boolean inString = false;

    /**
     * Whether or not the last char has been a backslash.
     */
    private boolean quoted = false;

    /**
     * Constructor for "dummy" instances.
     *
     * @see BaseFilterReader#BaseFilterReader()
     */
    public StripJavaComments() {
        super();
    }

    /**
     * Creates a new filtered reader.
     *
     * @param in A Reader object providing the underlying stream.
     *           Must not be <code>null.
     */
    public StripJavaComments(final Reader in) {
        super(in);
    }

    /**
     * Returns the next character in the filtered stream, not including
     * Java comments.
     *
     * @return the next character in the resulting stream, or -1
     * if the end of the resulting stream has been reached
     *
     * @exception IOException if the underlying stream throws an IOException
     * during reading
     */
    public int read() throws IOException {
        int ch = -1;
        if (readAheadCh != -1) {
            ch = readAheadCh;
            readAheadCh = -1;
        } else {
            ch = in.read();
            if (ch == '"' && !quoted) {
                inString = !inString;
                quoted = false;
            } else if (ch == '\\') {
                quoted = !quoted;
            } else {
                quoted = false;
                if (!inString) {
                    if (ch == '/') {
                        ch = in.read();
                        if (ch == '/') {
                            while (ch != '\n' && ch != -1 && ch != '\r') {
                                ch = in.read();
                            }
                        } else if (ch == '*') {
                            while (ch != -1) {
                                ch = in.read();
                                if (ch == '*') {
                                    ch = in.read();
                                    while (ch == '*' && ch != -1) {
                                        ch = in.read();
                                    }

                                    if (ch == '/') {
                                        ch = read();
                                        break;
                                    }
                                }
                            }
                        } else {
                            readAheadCh = ch;
                            ch = '/';
                        }
                    }
                }
            }
        }

        return ch;
    }

    /**
     * Creates a new StripJavaComments using the passed in
     * Reader for instantiation.
     *
     * @param rdr A Reader object providing the underlying stream.
     *            Must not be <code>null.
     *
     * @return a new filter based on this configuration, but filtering
     *         the specified reader
     */

    public Reader chain(final Reader rdr) {
        StripJavaComments newFilter = new StripJavaComments(rdr);
        return newFilter;
    }
}