Reader
Reader is an abstract class that defines Java's model of streaming character input. It
implements the Closeable and Readable interfaces. All of the methods in this class
(except for markSupported( )) will throw an IOException on error conditions. Table 19-3
provides a synopsis of the methods in Reader.
Writer
Writer is an abstract class that defines streaming character output. It implements the Closeable,
Flushable, and Appendable interfaces. All of the methods in this class throw an IOException
in the case of errors. Table 19-4 shows a synopsis of the methods in Writer.
FileReader
The FileReader class creates a Reader that you can use to read the contents of a file. Its two
most commonly used constructors are shown here:
FileReader(String filePath)
FileReader(File fileObj)
Either can throw a FileNotFoundException. Here, filePath is the full path name of a file, and
fileObj is a File object that describes the file.
The following example shows how to read lines from a file and print these to the standard
output stream. It reads its own source file, which must be in the current directory.
// Demonstrate FileReader.
import java.io.*;
class FileReaderDemo {
public static void main(String args[]) throws IOException {
FileReader fr = new FileReader("FileReaderDemo.java");
BufferedReader br = new BufferedReader(fr);
String s;
while((s = br.readLine()) != null) {
System.out.println(s);
}
fr.close();
}
}
FileWriter
FileWriter creates a Writer that you can use to write to a file. Its most commonly used
constructors are shown here:
FileWriter(String filePath)
FileWriter(String filePath, boolean append)
FileWriter(File fileObj)
FileWriter(File fileObj, boolean append)
They can throw an IOException. Here, filePath is the full path name of a file, and fileObj is a File
object that describes the file. If append is true, then output is appended to the end of the file.
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