How do I use a delimiter with Scanner useDelimiter in Java

Question

sc   new Scanner new File dataFile    sc useDelimiter     r n      I don t understand how delimiter works  can someone explain this in layman terms

User · Accepted Answer

The scanner can also use delimiters other than whitespace.

Easy example from Scanner API:

 String input = "1 fish 2 fish red fish blue fish";

 // \\s* means 0 or more repetitions of any whitespace character 
 // fish is the pattern to find
 Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");

 System.out.println(s.nextInt());   // prints: 1
 System.out.println(s.nextInt());   // prints: 2
 System.out.println(s.next());      // prints: red
 System.out.println(s.next());      // prints: blue

 // don't forget to close the scanner!!
 s.close();

The point is to understand the regular expressions (regex) inside the Scanner::useDelimiter. Find an useDelimiter tutorial here.

To start with regular expressions here you can find a nice tutorial.

Notes

abc…    Letters
123…    Digits
\d      Any Digit
\D      Any Non-digit character
.       Any Character
\.      Period
[abc]   Only a, b, or c
[^abc]  Not a, b, nor c
[a-z]   Characters a to z
[0-9]   Numbers 0 to 9
\w      Any Alphanumeric character
\W      Any Non-alphanumeric character
{m}     m Repetitions
{m,n}   m to n Repetitions
*       Zero or more repetitions
+       One or more repetitions
?       Optional character
\s      Any Whitespace
\S      Any Non-whitespace character
^…$     Starts and ends
(…)     Capture Group
(a(bc)) Capture Sub-group
(.*)    Capture all
(ab|cd) Matches ab or cd

User · Answer

With Scanner the default delimiters are the whitespace characters   But Scanner can define where a token starts and ends based on a set of delimiter  wich could be specified in two ways    Using the Scanner method  useDelimiter String pattern  Using the Scanner method   useDelimiter Pattern pattern  where Pattern is a regular expression that specifies the delimiter set    So useDelimiter   methods are used to tokenize the Scanner input  and behave like StringTokenizer class  take a look at these tutorials for further information    Setting Delimiters for Scanner Java util Scanner useDelimiter   Method   And here is an Example   public static void main String   args            Initialize Scanner object     Scanner scan   new Scanner  Anna Mills Female 18           initialize the string delimiter     scan useDelimiter              Printing the tokenized Strings     while scan hasNext             System out println scan next                  closing the scanner stream     scan close        Prints this output   Anna Mills Female 18

User · Answer

For example   String myInput   null  Scanner myscan   new Scanner System in  useDelimiter    n    System out println  Enter your input      myInput   myscan next    System out println myInput     This will let you use Enter as a delimiter   Thus  if you input   Hello world  ENTER    it will print  Hello World

[java] How do I use a delimiter with Scanner.useDelimiter in Java?

Notes

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