The user will enter a=(number here). I then want it to cut off the a= and retain the number. It works when I use s.next() but of course it makes me enter it two times which I don't want. With s.nextLine() I enter it once and the delimiter does not work. Why is this?
Scanner s = new Scanner(System.in);
s.useDelimiter("a=");
String n = s.nextLine();
System.out.println(n);
Because nextLine() doesn't care about delimiters. The delimiters only affect Scanner when you tell it to return tokens. nextLine() just returns whatever is left on the current line without caring about tokens.
A delimiter is not the way to go here; the purpose of delimiters is to tell the Scanner what can come between tokens, but you're trying to use it for a purpose it wasn't intended for. Instead:
String n = s.nextLine().replaceFirst("^a=","");
This inputs a line, then strips off a= if it appears at the beginning of the string (i.e. it replaces it with the empty string ""). replaceFirst takes a regular expression, and ^ means that it only matches if the a= is at the beginning of the string. This won't check to make sure the user actually entered a=; if you want to check this, your code will need to be a bit more complex, but the key thing here is that you want to use s.nextLine() to return a String, and then do whatever checking and manipulation you need on that String.
Try with StringTokenizer if Scanner#useDelimiter() is not suitable for your case.
Scanner s = new Scanner(System.in);
String n = s.nextLine();
StringTokenizer tokenizer = new StringTokenizer(n, "a=");
while (tokenizer.hasMoreTokens()) {
System.out.println(tokenizer.nextToken());
}
or try with String#split() method
for (String str : n.split("a=")) {
System.out.println(str);
}
input:
a=123a=546a=78a=9
output:
123
546
78
9
Related
My requirement is that I need to convert a string input taken from a Scanner's nextLine() method, to a string array:
My code:
Scanner sc= new Scanner(System.in);
String myString = sc.nextLine();
The above code works fine, when I give input in the console as : new String[]{"A:22","D:3","C:4","A:-22"}
but my challenge is to read scanner input and assign it to String array like this:
String[] consoleInput=sc.nextLine();
I have an incompatible type error, which is normal as String cannot be converted to String array. Is there a way to convert sc.nextLine() to String array in the above line?
If you literally type n, e, w, , S, etcetera (you type in new String[] {"A:22", "D:3"} and you want a method on scanner such that you get a string with that data), that is incredibly complicated and involves linking a java compiler in. If you're asking this kind of question, likely well beyond your current skill level.
What you can do, however, is simply ask the user to enter something like:
A:22 D:3 C:4 A:-22
Simply .nextLine().split(" ") and voila: First read a line, then split that line into a string array by looking for spaces as separators.
Scanner sc = new Scanner(System.in);
String myString = sc.nextLine();
String[] arr = myString.replaceAll("[ \"{}]", "").split(",");
Explanation:
The regex in replaceAll replaces the characters ", {, '}, and ` (space character) with an empty string. Then you simply split the string along all the commas, and you get a String array containing all the tokens the user entered.
Note: the regex removes all spaces as well, so if your tokens have spaces in them, then they will get removed. However, from what I gathered from your question, there won't be any spaces in the elements of the array.
Modified the regex pattern in replaceAll() method :
String[] strArr = s.nextLine().replaceAll("[ \"{}\\]\\[(new|String)]", "").split(",");
Output on printing the String Array strArr:
A:22
D:3
C:4
A:-22
User enters a string in java, I have to split it into different components.
Scanner scanner = new Scanner(System.in);
String test = scanner.next();
// split the test variable using the split method
String [] parts = test.split(" ,", 3);
s[i].setFirstName(parts[0].trim());
s[i].setlastName(parts[1].trim());
s[i].setID(Integer.parseInt(parts[2].trim()));
s[i].setgrade(Integer.parseInt(parts[3].trim()));
but it's not working. I can only get the first word to show up.
With your comment
I can get only one word to show up. it doesn't read any proceeding
words.
Use nextLine() instead of next().
next() will only return what comes before a space.
nextLine() automatically moves the scanner down after returning the current line.
name = scanner.nextLine();
Scanner doc
Use nextLine() rather than next() should fix the issue.
For further reference, take a look at the docs.
Change
String test = scanner.next();
to
String test = scanner.nextLine();
scanner.next() takes a word upto it encounters a blank space. nextLine() will consider the whole line.
I am trying to split the input sentence based on space between the words. It is not working as expected.
public static void main(String[] args) {
Scanner scaninput=new Scanner(System.in);
String inputSentence = scaninput.next();
String[] result=inputSentence.split("-");
// for(String iter:result) {
// System.out.println("iter:"+iter);
// }
System.out.println("result.length: "+result.length);
for (int count=0;count<result.length;count++) {
System.out.println("==");
System.out.println(result[count]);
}
}
It gives the output below when I use "-" in split:
fsfdsfsd-second-third
result.length: 3
==
fsfdsfsd
==
second
==
third
When I replace "-" with space " ", it gives the below output.
first second third
result.length: 1
==
first
Any suggestions as to what is the problem here? I have already referred to the stackoverflow post How to split a String by space, but it does not work.
Using split("\\s+") gives this output:
first second third
result.length: 1
==
first
Change
scanner.next()
To
scanner.nextLine()
From the javadoc
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace.
Calling next() returns the next word.
Calling nextLine() returns the next line.
The next() method of Scanner already splits the string on spaces, that is, it returns the next token, the string until the next string. So, if you add an appropriate println, you will see that inputSentence is equal to the first word, not the entire string.
Replace scanInput.next() with scanInput.nextLine().
The problem is that scaninput.next() will only read until the first whitespace character, so it's only pulling in the word first. So the split afterward accomplishes nothing.
Instead of using Scanner, I suggest using java.io.BufferedReader, which will let you read an entire line at once.
One more alternative is to go with buffered Reader class that works well.
String inputSentence;
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
inputSentence=br.readLine();
String[] result=inputSentence.split("\\s+");
rintln("result.length: "+result.length);
for(int count=0;count<result.length;count++)
{
System.out.println("==");
System.out.println(result[count]);
}
}
I am using a nested Scanner loop to extract the digit from a string line (from a text file) as follows:
String str = testString;
Scanner scanner = new Scanner(str);
while (scanner.hasNext()) {
String token = scanner.next();
// Here each token will be used
}
The problem is this code will skip all the spaces " ", but I also need to use those "spaces" too. So can Scanner return the spaces or I need to use something else?
My text file could contain something like this:
0
011
abc
d2d
sdwq
sda
Those blank lines contains 1 " " each, and those " " are what I need returned.
Use Scanner's hasNextLine() and nextLine() methods and you'll find your solution since this will allow you to capture empty or white-space lines.
By default, a scanner uses white space to separate tokens.
Use Scanner#nextLine method, 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.
To use a different token separator, invoke useDelimiter(), specifying
a regular expression. For example, suppose you wanted the token
separator to be a comma, optionally followed by white space. You would
invoke,
scanner.useDelimiter(",\\s*");
Read more from http://docs.oracle.com/javase/tutorial/essential/io/scanning.html
You have to understand what is a token. Read the documentation of Scanner:
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace.
You could use the nextLine() method to get the whole line and not "ignore" with any whitespace.
Better you could define what is a token by using the useDelimiter method.
This will work for you
Scanner scanner = new Scanner(new File("D:\\sample.txt"));
while (scanner.hasNextLine()) {
String token = scanner.nextLine();
System.out.println(token);
}
To use a more funtional approach you could use something like this:
String fileContent = new Scanner(new File("D:\\sample.txt"))
.useDelimiter("")
.tokens()
.reduce("", String::concat);
I am trying to use the Scanner class to read a line using the next(Pattern pattern) method to capture the text before the colon and then after the colon so that s1 = textbeforecolon and s2 = textaftercolon.
The line looks like this:
something:somethingelse
There are two ways of doing this, depending on specifically what you want.
If you want to split the entire input by colons, then you can use the useDelimiter() method, like others have pointed out:
// You could also say "scanner.useDelimiter(Pattern.compile(":"))", but
// that's the exact same thing as saying "scanner.useDelimiter(":")".
scanner.useDelimiter(":");
// Examines each token one at a time
while (scanner.hasNext())
{
String token = scanner.next();
// Do something with token here...
}
If you want to split each line by a colon, then it would be much easier to use String's split() method:
while (scanner.hasNextLine())
{
String[] parts = scanner.nextLine().split(":");
// The parts array now contains ["something", "somethingelse"]
}
I've never used Pattern with scanner.
I've always just changed the delimeter with a string.
http://java.sun.com/j2se/1.5.0/docs/api/java/util/Scanner.html#useDelimiter(java.lang.String)
File file = new File("someFileWithLinesContainingYourExampleText.txt");
Scanner s = new Scanner(file);
s.useDelimiter(":");
while (!s.hasNextLine()) {
while (s.hasNext()) {
String text = s.next();
System.out.println(text);
}
s.nextLine();
}