Re: How to detect blank input using Scanner?

Taria wrote:
We can't tell what you are doing without the code. A small, compilable
test program is always helpful especially if it doesn't do what you want.

Remember to compare Strings use .equals() not ==.

--

Knute Johnson

I thought the .equals would have worked! But it still produces the same result. I have included a small compilable portion of my program. All I want it to do is assign 'grades.dat' should the user hit the enter key.

import java.util.Scanner;

public class Test1 {

public static void main(String[] args) {

Scanner input = new Scanner(System.in);
System.out.print("Enter the names of your input file: <grades.dat> ");

// file to be read
String fileNameR = input.nextLine();

// if no input is given, defaults to "grades.dat"
if (fileNameR.equals(null)) {
fileNameR = "grades.dat";
}

System.out.print("\nProcessing " + fileNameR + ". \n");
}
}
// end program

The if statement is never evaluated to be true. Any help is appreciated.

Puzzled Marion


Puzzled:

Me too. It seems that Scanner doesn't detect the <ENTER> key being pressed. I don't know why and I don't have much call to use that class so I don't know a lot about it. Take a look at the program below. It does what you want but with different classes. Note the str.equals(""). There is a difference between a null and a "" String.

import java.io.*;

public class test6 {
public static void main(String[] args) throws IOException {
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);

String str = br.readLine();
if (str.equals(""))
System.out.println("default");
else
System.out.println(str);
}
}

--

Knute Johnson
email s/nospam/knute/
.

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