FileReader
The FileReader class creates a Reader that you can use to read the contents of a file for characters. Its two most commonly used constructors are shown here:
FileReader(String filePath)- filePath is the full path name of a file
FileReader(File fileObj)- fileObj is a File object that describes the file.
Methods inherited from class java.io.InputStreamReader
void close()- Closes the stream and releases any system resources associated with it.
String getEncoding()- Returns the name of the character encoding being used by this stream.
int read()- Reads a single character. The character read, or -1 if the end of the stream has been reached
int read(char[] cbuf, int offset, int length)- Reads characters into a portion of an array. The character read, or -1 if the end of the stream has been reached
boolean ready()- Tells whether this stream is ready to be read.
Methods inherited from class java.io.Reader
void mark(int readAheadLimit)- Marks the present position in the stream.
boolean markSupported()- Tells whether this stream supports the mark() operation.
void reset()- Resets the stream.
long skip(long n)- Skips characters.
Revised from Open JDK source code
import java.io.FileReader;
public class Main {
public static void main(String[] argv) throws Exception {
FileReader fr = new FileReader("text.txt");
int ch;
do {
ch = fr.read();
if (ch != -1)
System.out.println((char) ch);
} while (ch != -1);
fr.close();
}
}
The following code creates a FileReader from a filePath String
import java.io.FileReader;
public class MainClass {
public static void main(String args[]) {
try {
int counts[] = new int[10];
FileReader fr = new FileReader(args[0]);
int i;
while ((i = fr.read()) != -1) {
char c = (char) i;
int k = c - '0';
if (k >= 0 && k < 10)
++counts[k];
}
// Display digit counts
for (int j = 0; j < 10; j++) {
char c = (char) ('0' + j);
System.out.print(c + "=");
System.out.print(counts[j] + "; ");
}
fr.close();
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}