I have a application that needs to read a String buffer that is semi-colon ';' delimited.
String buff = foo.getBuff(); // returns the buffer
However, the buffer can get pretty large and I just need to get the last String token and then flush the temporary variable String buff so my app won't accumulate much memory.
Update:
I tried this code:
String lastToken = buff.substring(buff.lastIndexOf(";") + 1);
However, I am not getting result with this code above, compared to this:
List<String> slist = Arrays.asList(buff.split(";"));
String lastToken = slist.get(slist.size() - 1);
However using List is very slow. My web app is almost not responding when processing this.
This will help you:
String lastToken = buff.substring(buff.lastIndexOf(";") + 1);
I don't know Java, but by googling 2 functions, I think something like this should work:
String buff = foo.getBuff(); // returns the buffer
String lastToken = buff.substring(buff.lastIndexOf(";")+1);
Check this:
String lastToken = foo.getBuff().substring(foo.getBuff().lastIndexOf(';')+1);
Edit: Dan gave the answer better and faster than me.
Related
I have a .csv file that contains:
scenario, custom, master_data
1, ${CUSTOM}, A_1
I have a string:
a, b, c
and I want to replace 'custom' with 'a, b, c'. How can I do that and save to the existing .csv file?
Probably the easiest way is to read in one file and output to another file as you go, modifying it on a per-line basis
You could try something with tokenizers, this may not be completely correct for your output/input, but you can adapt it to your CSV file formatting
BufferedReader reader = new BufferedReader(new FileReader("input.csv"));
BufferedWriter writer = new BufferedWriter(new FileWriter("output.csv"));
String custom = "custom";
String replace = "a, b, c";
for(String line = reader.readLine(); line != null; line = reader.readLine())
{
String output = "";
StringTokenizer tokenizer = new StringTokenizer(line, ",");
for(String token = tokenizer.nextToken(); tokenizer.hasMoreTokens(); token = tokenizer.nextToken())
if(token.equals(custom)
output = "," + replace;
else
output = "," + token;
}
readInventory.close();
If this is for a one off thing, it also has the benefit of not having to research regular expressions (which are quite powerful and useful, good to know, but maybe for a later date?)
Have a look at Can you recommend a Java library for reading (and possibly writing) CSV files?
And once the values have been read, search for strings / value that start with ${ and end with }. Use Java Regular Expressions like \$\{(\w)\}. Then use some map for looking up the found key, and the related value. Java Properties would be a good candidate.
Then write a new csv file.
Since your replacement string is quite unique you can do it quickly without complicated parsing by just reading your file into a buffer, and then converting that buffer into a string. Replace all occurrences of the text you wish to replace with your target text. Then convert the string to a buffer and write that back to the file...
Pattern.quote is required because your string is a regular expression. If you don't quote it you may run into unexpected results.
Also it's generally not smart to overwrite your source file. Best is to create a new file then delete the old and rename the new to the old. Any error halfway will then not delete all your data.
final Path yourPath = Paths.get("Your path");
byte[] buff = Files.readAllBytes(yourPath);
String s = new String(buff, Charset.defaultCharset());
s = s.replaceAll(Pattern.quote("${CUSTOM}"), "a, b, c");
Files.write(yourPath, s.getBytes());
Hey guy's so am trying to replace all characters and numbers to get the /hello/what/ only without the REMOVEThis4.PNG i don't want to use string.replace("REMOVEThis4.PNG", ""); cause i wanna use it on other strings not only that
Any help is great my code
String sFile = "/hello/what/REMOVEThis4.PNG";
if (sFile.contains("/")){
String Replaced = sFile.replaceAll("(?s)", "");
System.out.println(Replaced);
}
I want the the output to be
/hello/what/
Only thanks alot!
If you are trying to parse a path, I recommend to find the last index of /, and get the substring to this index plus one. So
string = string.substring(0, string.lastIndexOf("/") + 1);
No need to use regular expressions in your case:
String sFile = "/hello/what/REMOVEThis4.PNG";
// TODO check actual last index of "/" against -1
System.out.println(sFile.substring(0, sFile.lastIndexOf("/") + 1));
Output
/hello/what/
Note
In case you are dealing with actual files, you can probably spare yourself the String manipulation and use File.getParent() instead:
File file = new File("/hello/what/REMOVEThis4.PNG");
System.out.println(file.getParent());
Output (may change depending on your system)
\hello\what
Use Java's File API:
String example = "/hello/what/REMOVEThis4.PNG";
File file = new File(example);
System.out.println(example);
String absolutePath = file.getAbsolutePath();
String filePath = absolutePath.substring(0, absolutePath.lastIndexOf(File.separator));
System.out.println(filePath);
Lets say I have a URL http://example.com/files/public_files/test.zip and I want to extract the last subpath so test.zip, How would I be able do this?
I am from Python so I am still new to Java and learning. In Python you could do something like this:
>>> x = "http://example.com/files/public_files/test.zip"
>>> x.split("/")[-1]
'test.zip'
There are many ways. I prefer:
String url = "http://example.com/files/public_files/test.zip";
String fileName = url.substring(url.lastIndexOf("/") + 1);
Using String class method is a way to go. But given that you are having a URL, you can use java.net.URL.getFile():
String url = "http://example.com/files/public_files/test.zip";
String filePart = new URL(url).getFile();
The above code will get you complete path. To get the file name, you can make use of Apache Commons - FilenameUtils.getName():
String url = "http://example.com/files/public_files/test.zip";
String fileName = FilenameUtils.getName(url);
Well, if you don't want to refer to 3rd party library for this task, String class is still an option to go for. I've just given another way.
you can use the following:
String url = "http://example.com/files/public_files/test.zip";
String arr[] = url.split("/");
String name = arr[arr.length - 1];
Most similar to the python syntax is :
String url = "http://example.com/files/public_files/test.zip";
String [] tokens = url.split("/");
String file = tokens[tokens.length-1];
Java lacks the convenient [-n] nth to last selector that Python has. If you wanted to do it all in one line, you'd have to do something gross like this:
String file = url.split("/")[url.split("/").length-1];
I don't recommend the latter
i have a dynamic String like
age/data/images/four_seasons1.jpg
from above string i need to get the image name alone (i.e.) four_seasons1.jpg
the path and the image will be a dynamic one(any image format will occure)
Please let me know how to do this in java?
thanks in advance
Use the File Object.
new File("/path/to/file").getName()
You could also use String.split().
"/path/to/file/sdf.png".split("/")
This will give you an array in which you pick the last element. But the File Object is better suited.
String text = "age/data/images/four_seasons1.jpg";
String name = text.substring(text.lastIndexOf("/") + 1);
String path = text.substring(0, text.lastIndexOf("/"));
System.out.println(name);
System.out.println(path);
Outputs
four_seasons1.jpg
age/data/images
Take some time and become familiar with the java.lang.String API. You'll be doing this kind of stuff a lot
You can go for regex but if you find the pattern is fixed, A very crude solution can be a straight forward approach
String url = "age/data/images/four_seasons1.jpg";
String imageName = url.substring(url.lastIndexOf( "/" )+1, url.length()) ;
You can parse this path. As a delimiter you must take '/' symbol. After that you can take last parsed element.
String phrase = "age/data/images/four_seasons1.jpg";
String delims = "/";
String[] tokens = phrase.split(delims);
About String.split you can read more here.
String s = "age/data/images/four_seasons1.jpg";
String fileName = new String();
String[] arr = s.split("/");
fileName = arr[arr.length-1];
}
My String containing a text file of 50 MB.
I got my String like this:
RandomAccessFile file = new RandomAccessFile("wiki.txt", "r");
FileChannel channel = file.getChannel();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, 1024*50);
byte[] b = new byte[1024*50];
buffer.get(b);
String wiki = new String(b);
I get a String expression that can contain multiple words, and I need to return an answer if this expression is in my wiki String (the big String) or not.
The action works good for about 1% of the String(from the beginning of the String), and when the phrase I'm looking for is in the middle or end of the String, the answer I get for the following code is a false:
System.out.println(wiki.contains(strToCheck));
System.out.println(wiki.indexOf(strToCheck, 0));
System.out.println(wiki.matches("(?i).*"+strToCheck+".*"));
Does anyone know why this happens?
Or what am I doing wrong?
Thank you.
I am sorry to say it but 1024*50 in not 50M. It is 50K.
It seems that you are reading 0.1% of your file and then searching in it.
you should try
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, 1024*1024*50);
because 50 MB = 1024*1024*50, 50kb = 1024 * 50, 1MB = 1024 kb`
Occam's razor: strToCheck is NOT in wiki.
If you are going to be performing searches in the String, you can consider implementing the Knuth–Morris–Pratt algorithm and buffering your reads of the original String so that the entire string is not loaded into memory.