Java find start of file name and extension

Question

HI, I have almost solved this but have now got stuck! What I need to do is look in a folder say..

String path = C://;

I then need a loop to see how many files are in that folder say 10. I need to look for files that start like

LAYER.EXE-******.pf

***** can change depending of other things but thats not important what is, is making sure when it finds a file that starts LAYER.EXE- it flags it up. Below is what I have been working on, I would vert much like you're help and thank you in advance! :)

 String path = "C://"; String files; File folder = new File(path); File[] listOfFiles = folder.listFiles(); for (int i = 0; i < listOfFiles.length; i++){ if (listOfFiles[i].isFile()){ files = listOfFiles[i].getName(); System.out.println(files); if (files == "LAYER.EXE.pf"){ System.out.println("found ================="); } } }

Vladimir Ivanov · Accepted Answer · 2011-01-31 14:47:42Z

files == "LAYER.EXE.pf"

change to

"LAYER.EXE.pf".equals(files)

What you do is a reference comparison, and you need the equality. Read more here.

Telling more, this will give you only the files which name is equal to "LAYER.EXE.pf".

Try files.startsWith("LAYER.");

Luciano Fiandesio · Accepted Answer · 2011-01-31 14:52:20Z

You can use FileNameFilter

public void listFiles() { File f = new File("C:/"); String[] allFiles = f.list(new MyFilter ()); for (String filez:allFiles ) { System.out.println(filez); } } class MyFilter implements FilenameFilter { @Override public boolean accept(final File dir, final String name) { return name.startsWith("LAYER.EXE.pf"); } }

Andreas Dolk · Accepted Answer · 2011-01-31 15:15:04Z

If you need to filter filenames, then consider using a filename filter:

File[] files = directory.listFiles(new FilenameFilter() { public boolean accept(File dir, String fileName) { return fileName.startsWith("LAYER.EXE-") && fileName.endsWith(".pf"); } });

This filter is based on your requirements and not on your current implementation.

The files array now only contains File objects whose the filenames are accepted by the filter, in other words, files that match the "pattern" LAYER.EXE-****.pf

Pablo Santa Cruz · Accepted Answer · 2011-01-31 14:49:17Z

If you need files that start with LAYER.EXE then you better change this:

if (files == "LAYER.EXE.pf")

Into:

if (files.startsWith("LAYER.EXE.pf"))

Please keep in mind that == operator on strings in Java won't behave as you might expect. Use equals or equalsIgnoreCase methods instead!

Dunaril · Accepted Answer · 2011-01-31 14:49:34Z

To check a String against another you should not use "==", but rather the equals method, or else you will compare the objects' references instead of the expressions. You can also use a better loop by making an iteration over your listOfFiles. Here is the corrected code :

String path = "C://"; String files; File folder = new File(path); File[] listOfFiles = folder.listFiles(); for (File checkedFile : listOfFiles){ if (checkedFile.isFile()){ files = checkedFile.getName(); System.out.println(files); if (files.equals("LAYER.EXE.pf")){ System.out.println("found ================="); } } }

SimonC · Accepted Answer · 2011-01-31 14:49:44Z

You want to compare the file names using one of the string comparisons, probably files.startsWith("LAYER.EXE.pf"). equals() (in this case) only returns true if the two objects are the same instance.

Jakob Nilsson-Ehle · Accepted Answer · 2011-01-31 14:52:03Z

First of all, for string comparisons in Java, you need to do .equals() instead of == as == will actually only evaluate to true if the strings are the same object, instead of comparing the values of the strings themselves.

So that would be if(files.equal("LAYER.EXE.pf"))"

Secondly, you should use the .startsWith() function to check if the first characters of a string matches another string

So, just do if(files.startsWith("LAYER.EXE")) and you should be fine

Sean Patrick Floyd · Accepted Answer · 2011-01-31 15:05:34Z

You can use a FileFilter to obtain only the files that fit your name pattern. Like this:

String path = "C://"; File folder = new File(path); File[] listOfFiles = folder.listFiles(new FileFilter(){ public boolean accept(File f){ return (f.startsWith("LAYER.EXE")); } });

And there you'll have an array with all the files you need, and only them. Next you can test if the array is void and if not handle the files.

Please don't use <code>, use the icon with the curly braces or indent your code with four spaces

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