Java Regex Help：在空格上拆分字符串，“=>”和逗号

Question

I need to split a string on any of the following sequences:

1 or more spaces
0 or more spaces, followed by a comma, followed by 0 or more spaces,
0 or more spaces, followed by "=>", followed by 0 or more spaces

Haven't had experience doing Java regexs before, so I'm a little confused. Thanks!

Example:
add r10,r12 => r10
store r10 => r1

Answer 1

Just create regex matching any of your three cases and pass it into split method:

string.split("\\s*(=>|,|\\s)\\s*");

Regex here means literally

1. Zero or more whitespaces ( \\\\s* )
2. Arrow, or comma, or whitespace ( =>|,|\\\\s )
3. Zero or more whitespaces ( \\\\s* )

You can replace whitespace \\\\s (detects spaces, tabs, line breaks, etc) with plain space character if necessary.

Answer 2

Strictly translated

For simplicity, I'm going to interpret you indication of "space" ( ) as "any whitespace" ( \\s ).

Translating your spec more or less "word for word" is to delimit on any of:

• 1 or more spaces
  • \\s+
• 0 or more spaces ( \\s* ), followed by a comma ( , ), followed by 0 or more spaces ( \\s* )
  • \\s*,\\s*
• 0 or more spaces ( \\s* ), followed by a "=>" ( => ), followed by 0 or more spaces ( \\s* )
  • \\s*=>\\s*

To match any of the above: (\\s+|\\s*,\\s*|\\s*=>\\s*)

Reduced form

However, your spec can be "reduced" to:

• 0 or more spaces
  • \\s* ,
• followed by either a space, comma, or "=>"
  • (\\s|,|=>)
• followed by 0 or more spaces
  • \\s*

Put it all together: \\s*(\\s|,|=>)\\s*

The reduced form gets around some corner cases with the strictly translated form that makes some unexpected empty "matches".

Code

Here's some code:

import java.util.regex.Pattern;

public class Temp {

    // Strictly translated form:
    //private static final String REGEX = "(\\s+|\\s*,\\s*|\\s*=>\\s*)";

    // "Reduced" form:
    private static final String REGEX = "\\s*(\\s|=>|,)\\s*";

    private static final String INPUT =
        "one two,three=>four , five   six   => seven,=>";

    public static void main(final String[] args) {
        final Pattern p = Pattern.compile(REGEX);
        final String[] items = p.split(INPUT);
        // Shorthand for above:
        // final String[] items = INPUT.split(REGEX);
        for(final String s : items) {
            System.out.println("Match: '"+s+"'");
        }
    }
}

Output:

Match: 'one'
Match: 'two'
Match: 'three'
Match: 'four'
Match: 'five'
Match: 'six'
Match: 'seven'

Answer 3

String[] splitArray = subjectString.split(" *(,|=>| ) *");

应该这样做。