CODEWITHSUNDEEP
javafilefilereader
user3012274
user3012274

Reputation: 1

Can anyone explain me how to read a file in java. what does -1 means? there no any numbers in the file i want to read.. confused :(

I cam across this code in my java class... but still i cannot understand how this code reads a file.. specially the while loop part...lecturer said if we do not implement loop.. this code reads only 1st letter of the file....

import java.io.FileReader;

public class NewClass {
    public static void main(String[] args)   {
        try{

            FileReader f1 = new FileReader("E:\\SOFTWARE setups\\Apache\\new.txt");
               while (true) {
                int x = f1.read();
                if (x == -1) {
                    break;
                }
                char y = (char) x;
                System.out.print(y);
            }

Upvotes: 0

Views: 142

Answers (3)

user2481237
user2481237

Reputation: 309

read() method reads single character, returns -1 when reaches to end of file.

While loop can be optimized and can be written like shown below 

int x;
while ( (x = f1.read()) !=-1) { 
    System.out.print((char)x);
}

Upvotes: 0

user2481237
user2481237

Reputation: 309

The read() method reads a single character, it returns either integer value of character or -1. Returns -1 if the end of the file has been reached.

Upvotes: 0

MD Sayem Ahmed
MD Sayem Ahmed

Reputation: 29166

From the documentation -

Reads a single character.

Returns the character read, or -1 if the end of the stream has been reached.

So yes, you need a for loop to read the entire content of your file. The basic strategy that your code is following is to read one character at a time, check to see if it's -1 (to see if end of file has been reached) and if not, print it on the console.

If you don't want to write a loop like this and read the whole content, then you can use some utility library like Apache Commons - 

File file = new File("E:\\SOFTWARE setups\\Apache\\new.txt");
String content = FileUtils.readFileToString(file);
System.out.print(content);

Upvotes: 2

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