Question

help!

Run the FileClient with the debugger (with a breakpoint on the line with while). You'll need to create a file called input.txt in the src folder (which the program will open) and add some (any) contents to it. Expand the inputFile Scanner variable in the debugger window to check out its stored data. How much of it can you make sense of? Watch the values of keep looping, next word, and inputFileScanner's buf field in the debugger as you step through the loop multiple times. In your documentation, address the following: • What do you think the Scanner's hasNext method does? • Theorize about what the while statement does. Try to create a different while statement that does something else. Use this code as a reference import java.io.File; import java.util.Scanner; class FileClient public static void main(String] args) throws java.io.FileNotFoundException File input File = new File("src/input.txt"); Scanner inputFileScanner = new Scanner(inputFile); while ( inputFileScanner.hasNext()) System.out.println(inputFileScanner.next());

Answer 1

First, let us analyze the code line by line and how can we improve it.

1.import java.io.File;
2.import java.util.Scanner;
3.class FileClient{
4.public static void main(String[]args) throws java.io.FileNotFoundException{
5.File inputFile=new File("src/input.txt");
6.Scanner inputFileScanner=new Scanner(inputFile);
7.while(inputFileScanner.hasNext()){
8.System.out.println(inputFileScanner.next());
}
}
}

Line 1 and 2 are used to import the library files in the program.

Line 3 has a definition of the main class.

Line 4 has the main method also , this program has an external dependency for a file. That is why we are specifying that if the file is not found or can't get accessed we should throw an exception and telling the java compiler to catch the exception.

Line no 5 is initializing the file to be read or written.

Line 6 is creating an instance of the Scanner class which takes the argument of a file object.

Line 7 is the while loop which we will discuss later.

//To write something in the file, there are a lot of ways, here I am mentioning one way..//

String content = "Some random content";

FileOutputStream writter = new FileOutputStream("src/input.txt");
DataOutputStream dataWritter= new DataOutputStream(new BufferedOutputStream(writter));
dataWritter.writeUTF(content);
  
dataOutStream.close();

• If we add this code in the above program we get...

package assing;

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;

public class FileClient {
public static void main(String[]args) throws java.io.FileNotFoundException{
File inputFile=new File("src/input.txt");
Scanner inputFileScanner=new Scanner(inputFile);
String content = "Some random content";
FileOutputStream writter = new FileOutputStream("src/input.txt");
DataOutputStream dataWritter= new DataOutputStream(new BufferedOutputStream(writter));
try {
   dataWritter.writeUTF(content);
} catch (IOException e) {

   e.printStackTrace();
}
try {
   dataWritter.close();
} catch (IOException e) {

   e.printStackTrace();
}
while(inputFileScanner.hasNext()){
try {
   System.out.println(inputFileScanner.next());
} catch (IOException e) {

   e.printStackTrace();
}
}
}
}

//now let's look at the questions//

• The scanner's hasNext() method is contained in the Java.util.Scanner class.The return value of the method is boolean.The function has two type of parameters.One we can pass a radix value.,in that case the method acts accordingly.In the other case the method does not takes any parameter as input.The working is as follow:

The method checks each contigious location for value other than null.Until null is found the method iterates until null is found.After each iteration it return value as true ,and when null is found ,return value is false.The method throws IllegalStateException .

• Basically, what a while loop does is that it loops or executes the set of commands within the loop brackets until the loop condition is false. The while function takes an argument, the loop is fully dependent on the argument.

In the above program, the hasNext() function always returns either true or false , basically a boolean value. The while loop continues to run until the value of the argument becomes false . In this case, until the file becomes empty, the while loop runs and prints the content of the file line after line in a separate line , until the file is fully read.

//Here is another example of the while loop//

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;

public class FileClient {
public static void main(String[]args) throws java.io.FileNotFoundException{
File inputFile=new File("src/input.txt");
Scanner inputFileScanner=new Scanner(inputFile);
String content = "Some random content";
FileOutputStream writter = new FileOutputStream("src/input.txt");
DataOutputStream dataWritter= new DataOutputStream(new BufferedOutputStream(writter));
try {
   dataWritter.writeUTF(content);
} catch (IOException e) {

   e.printStackTrace();
}
try {
   dataWritter.close();
} catch (IOException e) {

   e.printStackTrace();
}
while(inputFileScanner.hasNext()){
try {
   dataWritter.flush();
} catch (IOException e) {

   e.printStackTrace();
}
}
}
}

//Do comment for any queries......//