Remove all the multi-line comments from a block of text - Java java.lang

Java examples for java.lang:String Strip

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Description

Remove all the multi-line comments from a block of text

Demo Code

/*//from   w w w . java 2 s  .  c  o  m
 * Copyright 2005 Joe Walker
 *
 * Licensed 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 com.java2s;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;

public class Main {
    private static final String SPACE = " ";
    /**
     * How does a multi line comment start?
     */
    private static final String COMMENT_ML_START = "/*";
    /**
     * How does a multi line comment end?
     */
    private static final String COMMENT_ML_END = "*/";

    /**
     * Remove all the multi-line comments from a block of text
     * 
     * @param text
     *            The text to remove multi-line comments from
     * @return The multi-line comment free text
     */
    public static String stripMultiLineComments(String text) {
        if (text == null) {
            return null;
        }

        try {
            StringBuffer output = new StringBuffer();

            // Comment rules:
            /*
             * / This is still a comment /* /*
             */// Comments do not nest
              // /* */ This is in a comment
            /* // */// The second // is needed to make this a comment.
            // First we strip multi line comments. I think this is important:
            boolean inMultiLine = false;
            BufferedReader in = new BufferedReader(new StringReader(text));
            while (true) {
                String line = in.readLine();
                if (line == null) {
                    break;
                }

                if (!inMultiLine) {
                    // We are not in a multi-line comment, check for a start
                    int cstart = line.indexOf(COMMENT_ML_START);
                    if (cstart >= 0) {
                        // This could be a MLC on one line ...
                        int cend = line.indexOf(COMMENT_ML_END, cstart
                                + COMMENT_ML_START.length());
                        if (cend >= 0) {
                            // A comment that starts and ends on one line
                            // BUG: you can have more than 1 multi-line comment
                            // on a line
                            line = line.substring(0, cstart)
                                    + SPACE
                                    + line.substring(cend
                                            + COMMENT_ML_END.length());
                        } else {
                            // A real multi-line comment
                            inMultiLine = true;
                            line = line.substring(0, cstart) + SPACE;
                        }
                    } else {
                        // We are not in a multi line comment and we havn't
                        // started one so we are going to ignore closing
                        // comments even if they exist.
                    }
                } else {
                    // We are in a multi-line comment, check for the end
                    int cend = line.indexOf(COMMENT_ML_END);
                    if (cend >= 0) {
                        // End of comment
                        line = line.substring(cend
                                + COMMENT_ML_END.length());
                        inMultiLine = false;
                    } else {
                        // The comment continues
                        line = SPACE;
                    }
                }

                output.append(line);
                output.append('\n');
            }

            return output.toString();
        } catch (IOException ex) {
            // log.error("IOExecption unexpected.", ex);
            throw new IllegalArgumentException("IOExecption unexpected.");
        }
    }
}

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