IDE can't guess what your null is. Whether it is String or Charset. You can try something like:
String encoding=null;
FileUtils.readLines(file, encoding);
But I think that wouldn't work since readLines method needs to know what encoding your file uses. So if for example your file uses UTF-8, you can write this
FileUtils.readLines(file, StandardCharsets.UTF_8);
Or you can try to use default charset, see this: How to Find the Default Charset/Encoding in Java?
And as Apache docs say, deprecated version readLines(File file) used default charset. You can write this to get an equivalent:
FileUtils.readLines(file, Charset.defaultCharset());
Here's how to do it with Guava:
List<String> lines = Files.readLines(new File("myfile.txt"), Charsets.UTF_8);
Reference:
Files.readLines(File, Charset)
Using Apache Commons IO, you can use FileUtils#readLines method. It is as simple as:
List<String> lines = FileUtils.readLines(new File("..."));
for (String line : lines) {
System.out.println(line);
}
Apache Commons-IO has an IOUtils class as well as a FileUtils, which includes a readLines method similar to the one in FileUtils.
So you can use getResourceAsStream or getSystemResourceAsStream and pass the result of that to IOUtils.readLines to get a List<String> of the contents of your file:
List<String> myLines = IOUtils.readLines(ClassLoader.getSystemResourceAsStream("my_data_file.txt"));
I am assuming the file you want to read is a true resource on your classpath, and not simply some arbitrary file you could just access via new File("path_to_file");.
Try the following using ClassLoader, where resource is a String representation of the path to your resource file in your class path.
Valid String values for resource can include:
"foo.txt""com/company/bar.txt""com\\company\\bar.txt""\\com\\company\\bar.txt"
and path is not limited to com.company
Relevant code to get a File not in a JAR:
File file = null;
try {
URL url = null;
ClassLoader classLoader = {YourClass}.class.getClassLoader();
if (classLoader != null) {
url = classLoader.getResource(resource);
}
if (url == null) {
url = ClassLoader.getSystemResource(resource);
}
if (url != null) {
try {
file = new File(url.toURI());
} catch (URISyntaxException e) {
file = new File(url.getPath());
}
}
} catch (Exception ex) { /* handle it */ }
// file may be null
Alternately, if your resource is in a JAR, you will have to use Class.getResourceAsStream(resource); and cycle through the file using a BufferedReader to simulate the call to readLines().
Yes, you can do this in one line (though for robust IOException handling you wouldn't want to).
String content = new Scanner(new File("filename")).useDelimiter("\\Z").next();
System.out.println(content);
This uses a java.util.Scanner, telling it to delimit the input with \Z, which is the end of the string anchor. This ultimately makes the input have one actual token, which is the entire file, so it can be read with one call to next().
There is a constructor that takes a File and a String charSetName (among many other overloads). These two constructor may throw FileNotFoundException, but like all Scanner methods, no IOException can be thrown beyond these constructors.
You can query the Scanner itself through the ioException() method if an IOException occurred or not. You may also want to explicitly close() the Scanner after you read the content, so perhaps storing the Scanner reference in a local variable is best.
See also
- Java Tutorials - I/O Essentials - Scanning and formatting
Related questions
- Validating input using java.util.Scanner - has many examples of more typical usage
Third-party library options
For completeness, these are some really good options if you have these very reputable and highly useful third party libraries:
Guava
com.google.common.io.Files contains many useful methods. The pertinent ones here are:
String toString(File, Charset)- Using the given character set, reads all characters from a file into a
String
- Using the given character set, reads all characters from a file into a
List<String> readLines(File, Charset)- ... reads all of the lines from a file into a
List<String>, one entry per line
- ... reads all of the lines from a file into a
Apache Commons/IO
org.apache.commons.io.IOUtils also offer similar functionality:
String toString(InputStream, String encoding)- Using the specified character encoding, gets the contents of an
InputStreamas aString
- Using the specified character encoding, gets the contents of an
List readLines(InputStream, String encoding)- ... as a (raw)
ListofString, one entry per line
- ... as a (raw)
Related questions
Most useful free third party Java libraries (deleted)?
From Java 7 (API Description) onwards you can do:
new String(Files.readAllBytes(Paths.get(filePath)), StandardCharsets.UTF_8);
Where filePath is a String representing the file you want to load.