I am Writing a java program to remove the comments in the same java program. I am thinking of using a file reader. But I'm not sure whether it will work.
Because two process will be using the same file.
But I think before executing the code, java file will make a .class file.
So if I use a filereader to edit the java file. It should not give me error that another process is already using this file.
Am I thinking correct?
Thanks in advance.
Yes, you can do that without any problems.
Note: Be careful with things like:
String notAComment = "// This is not a comment";
If you just want to remove comments from a Java program, why don't you do a simple search and replace using a regex, and convert all comments into an empty string?
Here's a verbose way of doing it, in Java:
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.BufferedReader;
class Cleaner{
public static void main( String a[] )
{
String source = readFile("source.java");
System.out.println(source.replaceAll("(?:/\\*(?:[^*]|(?:\\*+[^*/]))*\\*+/)|(?://.*)",""));
}
static String readFile(String fileName) {
File file = new File(fileName);
char[] buffer = null;
try {
BufferedReader bufferedReader = new BufferedReader( new FileReader(file));
buffer = new char[(int)file.length()];
int i = 0;
int c = bufferedReader.read();
while (c != -1) {
buffer[i++] = (char)c;
c = bufferedReader.read();
}
} catch (IOException e) {
e.printStackTrace();
}
return new String(buffer);
}
}
You are right, the are not two processes using the same file, your program will use the .class files and process the .java files. You may want to take a closer look at this page:
Finding Comments in Source Code Using Regular Expressions
Yes, using a FileReader will work. One thing to watch out is the FileEncoding if you might have non-English characters or work across different platforms. In Eclipse and other IDEs you can change the character set for a Java source file to different encodings. If unsure, it might be worth using:
InputStream in = ....
BufferedReader r = new BufferedReader(new InputStreamReader(in, "UTF-8"));
..
and likewise when you are writing the output back out, use an OutputStreamWriter with UTF-8.
Its late but it may help some to remove all types of comments.
package com.example;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
class CommentRemover {
public static void main(String a[]) {
File file = new File("F:/Java Examples/Sample.java");
String fileString = readLineByLine(file);
fileString = fileString.replaceAll(
"(?:/\\*(?:[^*]|(?:\\*+[^*/]))*\\*+/)", "");
System.out.println(fileString);
}
private static String readLineByLine(File file) {
String textFile = "";
FileInputStream fstream;
try {
fstream = new FileInputStream(file);
BufferedReader br = new BufferedReader(new InputStreamReader(
fstream));
String strLine;
while ((strLine = br.readLine()) != null) {
textFile = textFile + replaceComments(strLine) + "\n";
}
br.close();
} catch (Exception e) {
e.printStackTrace();
}
return textFile;
}
private static String replaceComments(String strLine) {
if (strLine.startsWith("//")) {
return "";
} else if (strLine.contains("//")) {
if (strLine.contains("\"")) {
int lastIndex = strLine.lastIndexOf("\"");
int lastIndexComment = strLine.lastIndexOf("//");
if (lastIndexComment > lastIndex) { // ( "" // )
strLine = strLine.substring(0, lastIndexComment);
}
} else {
int index = strLine.lastIndexOf("//");
strLine = strLine.substring(0, index);
}
}
return strLine;
}
}
Have a look at the post Remove comments from String for doing your stuff. You may use either FileReader or java.util.Scanner class to read the file.
I made a open source library (CommentRemover on GitHub) for this necessity , you can remove single line and multiple line Java Comments.
It supports remove or NOT remove TODO's.
Also it supports JavaScript , HTML , CSS , Properties , JSP and XML Comments too.
Little code snippet how to use it (There is 2 type usage):
First way InternalPath
public static void main(String[] args) throws CommentRemoverException {
// root dir is: /Users/user/Projects/MyProject
// example for startInternalPath
CommentRemover commentRemover = new CommentRemover.CommentRemoverBuilder()
.removeJava(true) // Remove Java file Comments....
.removeJavaScript(true) // Remove JavaScript file Comments....
.removeJSP(true) // etc.. goes like that
.removeTodos(false) // Do Not Touch Todos (leave them alone)
.removeSingleLines(true) // Remove single line type comments
.removeMultiLines(true) // Remove multiple type comments
.startInternalPath("src.main.app") // Starts from {rootDir}/src/main/app , leave it empty string when you want to start from root dir
.setExcludePackages(new String[]{"src.main.java.app.pattern"}) // Refers to {rootDir}/src/main/java/app/pattern and skips this directory
.build();
CommentProcessor commentProcessor = new CommentProcessor(commentRemover);
commentProcessor.start();
}
Second way ExternalPath
public static void main(String[] args) throws CommentRemoverException {
// example for externalInternalPath
CommentRemover commentRemover = new CommentRemover.CommentRemoverBuilder()
.removeJava(true) // Remove Java file Comments....
.removeJavaScript(true) // Remove JavaScript file Comments....
.removeJSP(true) // etc..
.removeTodos(true) // Remove todos
.removeSingleLines(false) // Do not remove single line type comments
.removeMultiLines(true) // Remove multiple type comments
.startExternalPath("/Users/user/Projects/MyOtherProject")// Give it full path for external directories
.setExcludePackages(new String[]{"src.main.java.model"}) // Refers to /Users/user/Projects/MyOtherProject/src/main/java/model and skips this directory.
.build();
CommentProcessor commentProcessor = new CommentProcessor(commentRemover);
commentProcessor.start();
}
public class Copy {
void RemoveComments(String inputFilePath, String outputFilePath) throws FileNotFoundException, IOException {
File in = new File(inputFilePath);
File out = new File(outputFilePath);
BufferedReader bufferedreader = new BufferedReader(new FileReader(in));
PrintWriter pw = new PrintWriter(new FileWriter(out));
String line = null, lineToRemove = null;
while ((line = bufferedreader.readLine()) != null) {
if (line.startsWith("/*") && line.endsWith("*/")) {
lineToRemove = line;
}
if (!line.trim().equals(lineToRemove)) {
pw.println(line);
pw.flush();
}
}
}
}
