Replace substring with replacement string
I am trying to write a small program that detects comments in a code file, and tag them with an index-tag, which means an incrementing tag.
For example, this input:
method int foo (int y) {
int temp; // FIRST COMMENT
temp = 63; // SECOND COMMENT
// THIRD COMMENT
}
should be changed to:
method int foo (int y) {
int temp; <TAG_0>// FIRST COMMENT</TAG>
temp = 63; <TAG_1>// SECOND COMMENT</TAG>
<TAG_2>// THIRD COMMENT</TAG>
}
I tried the following code:
String prefix, suffix;
String pattern = "(//.*)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(fileText);
int i = 0;
suffix = "</TAG>";
while (m.find()) {
prefix = "<TAG_" + i + ">";
System.out.println(m.replaceAll(prefix + m.group() + suffix));
i++;
}
Output for the above code:
method int foo (int y) {
int temp; <TAG_0>// FIRST COMMENT</TAG>
temp = 63; <TAG_0>// SECOND COMMENT</TAG>
<TAG_0>// THIRD COMMENT</TAG>
}
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To replace the occurrence of detected patterns, you must use a method Matcher#appendReplacement
that fills in StringBuffer
:
StringBuffer sb = new StringBuffer();
while (m.find()) {
prefix = "<TAG_" + i + ">";
m.appendReplacement(sb, prefix + m.group() + suffix);
i++;
}
m.appendTail(sb); // append the rest of the contents
The reason replaceAll
will result in an incorrect substitution as it will check the Matcher
entire string to replace each matched pattern with <TAG_0>...</TAG>
. In fact, the loop will only run once.
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Have you tried reading the file in line, for example:
String prefix, suffix;
suffix = " </TAG>";
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
int i = 0;
for (String line; (line = br.readLine()) != null;) {
if (line.contains("//")) {
prefix = "<TAG_" + i + ">//";
System.out.println(line.split("//*")[0] + " " + prefix + line.split("//*")[1] + suffix);
i++;
}
}
} catch (IOException e) {
}
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fichiertexte.txt:
method int foo (int y) {
int temp; // FIRST COMMENT
temp = 63; // SECOND COMMENT
// THIRD COMMENT
}
App.java:
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class App {
public static void main(String[] args) {
String fileText = "";
String fichier = "fichiertexte.txt";
// lecture du fichier texte
try {
InputStream ips = new FileInputStream(fichier);
InputStreamReader ipsr = new InputStreamReader(ips);
BufferedReader br = new BufferedReader(ipsr);
String ligne;
while ((ligne = br.readLine()) != null) {
//System.out.println(ligne);
fileText += ligne + "\n";
}
br.close();
} catch (Exception e) {
System.err.println(e.toString());
}
String prefix, suffix;
String pattern = "(//.*)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(fileText);
int i = 0;
suffix = "</TAG>";
StringBuffer sb = new StringBuffer();
while (m.find()) {
prefix = "<TAG_" + i + ">";
m.appendReplacement(sb, prefix + m.group() + suffix);
i++;
}
System.out.println(sb.toString());
}
}
System.out:
method int foo (int y) {
int temp; <TAG_0>// FIRST COMMENT</TAG>
temp = 63; <TAG_1>// SECOND COMMENT</TAG>
<TAG_2>// THIRD COMMENT</TAG>
}
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