FileReader Java - How to use FileReader in Java and what to import for FileReader class and methods with Java FileReader Examples
FileReader in Java
FileReader in Java is a class that we use to read data from a file. It is character-oriented and returns data in the form of bytes. This class is part of the java.io package and extends the InputStreamReader class.
Java FileReader constructors
The FileReader class supports two types of constructors: FileReader(String file): Opens the specified file using the filename as a string. FileReader(File f): Opens the specified file using the filename as a File Object. Both the constructors throw FileNotFoundException if the specified file is not present.
Java FileReader methods
Below is the list of methods that the FileReader class supports for reading data from the file.
Java FileReader Examples
Read a character using the FileReader The read() method of the FileReader class in Java reads a single character at a time from the file. Below is the example that shows to read a single character. The InputFile contains the test "FileReader example". Hence the first output is 'F' and the second output is 'i'. import java.io.FileReader; import java.io.IOException; public class ReadFileDemo { public static void main(String args) throws IOException { FileReader fr = new FileReader("InputFile.txt"); char ch = (char)fr.read(); System.out.println("Single character read: " + ch); System.out.println("Single character read: " + (char)fr.read()); fr.close(); } } Single character read: F Single character read: i Read an array of characters using FileReader In the below example, we read the full content of the file using the read() method of Java FileReader. We can achieve this by calling the read method within a while loop so that it reads individual characters until it reaches the end of the file. When there are no characters to read, the read() method returns -1. import java.io.FileReader; import java.io.IOException; public class ReadFileDemo { public static void main(String args) throws IOException { FileReader fr = new FileReader("InputFile.txt"); //Read all content int i; System.out.println("File content:"); while((i=fr.read())!=-1) System.out.print((char)i); fr.close(); } } File content: FileReader example Read the specific length of characters In the below example, we can how to read a specific length of characters(which is 5 in this case) from the file using the read() method. We can specify the starting position to read along with the number of characters to be read. Hence it prints the output with 5 characters which is 'FileR' where the input file content is "FileReader example". import java.io.FileReader; import java.io.IOException; public class ReadFileDemo { public static void main(String args) throws IOException { FileReader fr = new FileReader("InputFile.txt"); //Read specific length of characters char ch = new char; int i = fr.read(ch, 0, 5); System.out.println("Number of characters read: " + i); for(char c : ch) { System.out.print(c); } fr.close(); } } Number of characters read: 5 FileR Skip and read characters using FileReader The skip() method of the Java FileReader class skips the specified number of characters and reads the remaining characters. In this example, we skip the first 4 characters and then read from the 5th character until the end of the file. Hence when the InputFile contains "FileReader example" as the content, it prints only "Reader example" as the output. import java.io.FileReader; import java.io.IOException; public class ReadFileDemo { public static void main(String args) throws IOException { FileReader fr = new FileReader("InputFile.txt"); //Skip and read fr.skip(4); System.out.println("Content after skipping 4 characters:"); int i; while((i=fr.read())!=-1) System.out.print((char)i); fr.close(); } } Content after skipping 4 characters: Reader example  Reference Read the full article
