Thread: Dont quite understand how Scanner.nextLine() works

Hi,

see here:

firstChoice = new Scanner(System.in);
 
		System.out.println("You chose " + firstChoice.nextLine());

I know what happens, I'm giving my Scanner object the parameter of the keyboard input and then I am outputting "You chose" plus what the user has typed in. My question is what exactly does the nextLine method do to print out my Scanner objects parameter?

I have read it "advances this scanner past the current line and returns the input that was skipped.", as I'm a beginner could you explain in simply terms what this method does to display the objects parameter.

Thanks.

what exactly does the nextLine method do to print out my Scanner objects parameter?

The nextLine method returns a String value. It does not print out anything. Where it gets that String is determined by how the Scanner class is created. It can read from the console, from a String or from a disk file.
The System.out.println method does the printing.

Thanks for the reply.

I understand that system.out.print is doing the actually printing.

Im still confused, answer me this, when I put...

firstChoice = new Scanner(System.in);
 
		System.out.println(firstChoice.nextLine());

...it prints out what i type in, but when i put...

firstChoice = new Scanner(System.in);
 
		System.out.println(firstChoice);

...it prints "java.util.Scanner[delimiters=\p{javaWhitespace}+][position=0][match valid=false][need input=false][source closed=false][skipped=false][group separator=\,][decimal separator=\.][positive prefix=][negative prefix=\Q-\E][positive suffix=][negative suffix=][NaN string=\Q?\E][infinity string=\Q?\E]".

So by using the nextLine() method, it changes the output from that to what I actually input.

firstChoice is an instance of the Scanner class. When you print it, the instance's toString method returns information about how the Scanner class instance has been initialized. It has nothing to do with the data that the Scanner object is reading.

by using the nextLine() method, it changes the output

Read the Scanner class's API doc for the nextLine method to see what it returns.

Its doc say:

"Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line.
Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.


Returns:
the line that was skipped"

How does nextLine() method change the output?

How does nextLine() method change the output?

Where is the "output" you are asking about?
The nextLine method returns a String.
Inside of the Scanner class instance there are pointers and buffers that handle what the user has typed in at the console. Those will be changed when nextLine is called.

Just checking, when we print a method by putting "System.out.print(exampleMethod);" are we printing the methods return value?

when we print a method by putting "System.out.print(exampleMethod);

That code is NOT a method call. To call a method you put () after it:
System.out.print(exampleMethod());

are we printing the method's returned value?

Yes.

Oh yeah, I forgot to add the brackets then, my bad

Thanks, its clearer now.

What exactly is returned from nextLine tho, is it the object parameter, which was the keyboard input we gave it earlier?

What exactly is returned from nextLine

Two places to see:
1) read the API doc
2) execute it, save it what it returns in a variable and print out the variable or examine the variables contents with some methods.

Am I right in saying basically this nextLine() method is made to pause and wait until it gets input from the scanner objects parameter. If the objects parameter already has input such as ("hi") then it will output that, however if the objects parameter is (System.in) then it will wait until the user enters text.

Right?

Try writing a small test program and try all the combinations that you can think of to see how it works.

I have played with it, and thats what ive come with, was i wrong then? :S

What you said sounds about right.
I can't argue with a program's results. If you have a program that you don't understand what it is doing, post the program and the console where you executed it and your questions.

To copy the contents of the command prompt window:
Click on Icon in upper left corner
Select Edit
Select 'Select All' - The selection will show
Click in upper left again
Select Edit and click 'Copy'

Paste here.

Thanks

I know how to use it but i was just trying to find out its inner workings