Java write() Method to echo System.in to System.out

The fundamental method of the OutputStream class is write().
This method writes a single unsigned byte of data whose value should be between 0 and 255. If you pass a number larger than 255 or smaller than zero, it is reduced modulo 256 before being written. The following code fragment prints the printable ASCII characters between 32 and 127 on System.out:

for (int i = 32; i < 128; i++) {
  System.out.write(i);
  System.out.println();
}

In this example, the console interprets the numeric values as ASCII characters, not as numbers. This is a feature of the console, not of the OutputStream class or the specific subclass of which System.out is an instance. The write() method merely sends a particular bit pattern to a particular output stream. How that bit pattern is interpreted depends on what's connected to the other end of the stream.
The write() method is declared to throw an IOException. java.io.IOException is a checked exception so you will need to wrap most calls to this method in a try-catch block or declare that your own method throws IOException.

The write() method is declared to throw an IOException. java.io.IOException is a checked exception so you will need to wrap most calls to this method in a try-catch block or declare that your own method throws IOException.

try {
  for (int i = 32; i < 128; i++) {
    os.write(i);
}
catch (IOException e) {
  System.err.println(e);
}

The one notable exception is System.out. For reasons that will be discussed in the next lesson, no method invocation on System.out will ever throw an exception.

Given the following code :

1. import java.io.FileInputStream;
2. //Codes
4. public class Stream{
5.   public static void main(String[] args) throws IOException {
7.     FileInputStream in = null;
8.     FileOutputStream out = null;
10.   try {
11.     in = new FileInputStream("source.txt");
12.     out = new FileOutputStream("dest.txt");
13.     int c;
15.     while ((c = in.read()) != -1) {
16.       out.write(c);
17. 	  }
18. 	} finally {
19.        if (in != null) {
20.          in.close();
21.        }
22.        if (out != null) {
23.          out.close();
24. 	     }
25.     }
26.   }
27. }
 

Which are true? (Select two options.)

1. We have to import java.io.FileOutputStream and java.io.IOException Compilation to succeed.
2. Importing only java.io.FileOutputStream is enough Compilation to succeed.
3. Importing only java.io.IOException is enough Compilation to succeed.
4. java.io.FileInputStream is enough Compilation to succeed.
5. Changing import java.io.FileInputStream; to import java.io.*; will make this code works.

Option A is correct because at line 5,

public static void main(String[] args) throws IOException {  

needs the java.io.IOException class and we need the java.io.FileOutputStream class to write data to files (line 8), so we need these two classes to make this code work. We can achieve this by importing all classes in java.io package by using import java.io.*; since it will import all the classes including these two, so option E is correct.
Option B is incorrect because we need to import both FileOutputStream and IOException classes or none of these will ensure correct compilation. So answers B, C and D are incorrect.
See http://docs.oracle.com/javase/tutorial/essential/io/bytestreams.html for more information. The correct answer is: We have to import java.io.FileOutputStream and java.io.IOException in order to make compilation succeed. Changing import java.io.FileInputStream; to import java.io.*; will make this code work.

Click on the Exercise link below to write a program that reads data from System.in, and copies each byte read to System.out as a byte.
Java Write Method - Exercise