Difference between FileInputStream and FileReader in Java | InputStream vs Reader

Before going to explain specific difference between FileInputStream and FileReader in Java, I would like to state fundamental difference between an InputStream and a Reader in Java, and when to use InputStream and when to go for Reader. Actually, Both InputStream and Reader are abstractions to read data from source, which can be either file or socket, but main difference between them is, InputStream is used to read binary data, while Reader is used to read text data, precisely Unicode characters. So what is difference between binary and text data? well everything you read is essentially bytes, but to convert a byte to text, you need a character encoding scheme. Reader classes uses character encoding to decode bytes and return characters to caller. Reader can either use default character encoding of platform on which your Java program is running or accept a Charset object or name of character encoding in String format e.g. "UTF-8". Despite being one of the simplest concept, lots of Java developers make mistakes of not specifying character encoding, while reading text files or text data from socket. Remember, if you don't specify correct encoding, or your program is not using character encoding already present in protocol e.g. encoding specified in "Content-Type" for HTML files and encoding presents in header of XML files, you may not read all data correctly. Some characters which are not present in default encoding, may come up as ? or little square. Once you know this fundamental difference between stream and reader, understanding difference between FileInputStream and FileReader is quite easy. Both allows you to read data from File, but FileInputStream is used to read binary data, while FileReader is used to read character data.

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