Reading & Writing Files - Java Questions & Answers

This section of our 1000+ Java MCQs focuses on reading & writing files in Java Programming Language.

1. Which of these class contains the methods used to write in a file?
a) FileStream
b) FileInputStream
c) BufferedOutputStream
d) FileBufferStream
View Answer

Answer: b
Explanation: BufferedOutputStream Provides buffering for output streams, which helps to improve efficiency by reducing the number of write operations to the underlying file.

2. Which of these exception is thrown in cases when the file specified for writing is not found?
a) IOException
b) FileException
c) FileNotFoundException
d) FileInputException
View Answer

Answer: c
Explanation: In cases when the file specified is not found, then FileNotFoundException is thrown by java run-time system, earlier versions of java used to throw IOException but after Java 2.0 they throw FileNotFoundException.

3. Which of these methods are used to read in from file?
a) get()
b) read()
c) scan()
d) readFileInput()
View Answer

Answer: b
Explanation: Each time read() is called, it reads a single byte from the file and returns the byte as an integer value. read() returns -1 when the end of the file is encountered.

4. Which of these values is returned by read() method is end of file (EOF) is encountered?
a) 0
b) 1
c) -1
d) Null
View Answer

Answer: c
Explanation: Each time read() is called, it reads a single byte from the file and returns the byte as an integer value. read() returns -1 when the end of the file is encountered.

5. Which of these exception is thrown by close() and read() methods?
a) IOException
b) FileException
c) FileNotFoundException
d) FileInputOutputException
View Answer

Answer: a
Explanation: Both close() and read() method throw IOException.

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6. Which of these methods is used to write() into a file?
a) put()
b) putFile()
c) write()
d) writeFile()
View Answer

Answer: c
Explanation: The write() method is used to write data into a file. Specifically, the write() method of the FileWriter class is commonly used for this purpose.

7. What will be the output of the following Java program?

```
   import java.io.*;
```
```
   class filesinputoutput
```
```
   {
```

       public static void main(String args[]) throws Exception

```
       {
```

           InputStream obj = new FileInputStream("inputoutput.java");

           System.out.print(obj.available());

```
       }
```
```
   }
```

Note: inputoutput.java is stored in the disk.
a) true
b) false
c) prints number of bytes in file
d) prints number of characters in the file
View Answer

Answer: c
Explanation: obj.available() returns the number of bytes.
Output:

$ javac filesinputoutput.java
$ java filesinputoutput
1422

(Output will be different in your case)

8. What will be the output of the following Java program?

```
import java.io.*;
```
```
public class filesinputoutput
```
```
{
```

    public static void main(String[] args)

```
    {
```
```
        String obj  = "abc";
```
```
        byte b[] = obj.getBytes();
```

        ByteArrayInputStream obj1 = new ByteArrayInputStream(b);

```
        for (int i = 0; i < 2; ++ i)
```
```
        {
```
```
            int c;
```

            while((c = obj1.read()) != -1)

```
            {
```
```
                if(i == 0)
```
```
                {
```

                    System.out.print(Character.toUpperCase((char)c));

```
                }
```

                System.out.print((char)c);

```
            }
```
```
        }
```
```
    }
```
```
}
```

a) AaBaCa
b) ABCaaa
c) AaaBaaCaa
d) AaBbCc
View Answer

Answer: d
Explanation: The String object is converted to array of bytes and create a object of ByteArrayInputStream and read from the object byte by byte in an integer and printed by parsing the character to uppercase followed by lowercase.
Output:

$ javac filesinputoutput.java
$ java filesinputoutput
AaBaaCaaa

9. What will be the output of the following Java program?

```
    import java.io.*;
```
```
    class Chararrayinput
```
```
    {
```

        public static void main(String[] args)

```
        {
```
```
	    String obj  = "abcdef";
```
```
            int length = obj.length();
```

            char c[] = new char[length];

            obj.getChars(0, length, c, 0);

            CharArrayReader input1 = new CharArrayReader(c);

            CharArrayReader input2 = new CharArrayReader(c, 0, 3);

```
            int i;
```
```
            try
```
```
            {
```
```
		while((i = input2.read()) != -1)
```
```
                {
```

                    System.out.print((char)i);

```
                }
```
```
       	    } 
```
```
            catch (IOException e)
```
```
            {
```
```
                e.printStackTrace();
```
```
	    }
```
```
	}
```
```
    }
```

a) abc
b) abcd
c) abcde
d) abcdef
View Answer

Answer: a
Explanation: The input2 object contains the first three characters from the character array; later, each of these characters is printed one by one.
Output:

$ javac Chararrayinput.java
$ java Chararrayinput
abc

10. What will be the output of the following Java program?

```
    import java.io.*;
```
```
    class Chararrayinput
```
```
    {
```

        public static void main(String[] args)

```
        {
```
```
	    String obj  = "abcdefgh";
```
```
            int length = obj.length();
```

            char c[] = new char[length];

            obj.getChars(0, length, c, 0);

            CharArrayReader input1 = new CharArrayReader(c);

            CharArrayReader input2 = new CharArrayReader(c, 1, 4);

```
            int i;
```
```
            int j;
```
```
            try 
```
```
            {
```

		while((i = input1.read()) == (j = input2.read()))

```
                {
```

                    System.out.print((char)i);

```
                }
```
```
       	    } 
```
```
            catch (IOException e)
```
```
            {
```
```
                e.printStackTrace();
```
```
	    }
```
```
	}
```
```
    }
```

a) abc
b) abcd
c) abcde
d) none of the mentioned
View Answer

Answer: d
Explanation: No output is printed. CharArrayReader object input1 contains string “abcdefgh” whereas object input2 contains string “bcde”, when while((i=input1.read())==(j=input2.read())) is executed the starting character of each object is compared since they are unequal control comes out of loop and nothing is printed on the screen.
Output:

$ javac Chararrayinput.java
$ java Chararrayinput

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