Question

I currently have the following string in java:

"Blah, blah, blah,~Part One, Part Two~,blah blah"

I need to remove the comma between the ~ character so it reads.

"Blah, blah, blah,~Part One Part Two~,blah blah"

Can anyone help me out please?

Many thanks,

Answer 1

    String[] tests = {
        "a,b,c,d,e,f",
        "a,b,~c~,d,e",
        "~a,b,c,d,e~",
        "a,b,c,~d,e,f~,g,h,i,~j,k,l,~m,n,o~,q,r,~s,t,u",
    };
    for (String test : tests) {
        System.out.println(
            test.replaceAll(
                "(^[^~]*~)|([^~]*$)|([^,~]*),|([^,~]*~[^~]*~)",
                "$1$2$3$4"
            )
        );
    }

The above prints:

a,b,c,d,e,f
a,b,~c~,d,e
~abcde~
a,b,c,~def~,g,h,i,~jkl~m,n,o~qr~s,t,u

How it works

There are 4 cases:

• We’re at the beginning of the string, “outside”
  • Just match until we find the first ~, so next time we’ll be “inside”
  • So, (^[^~]*~)
• There are no more ~ till the end of the string
  • If there are even number of ~, we’ll be “outside”
  • Just match until the end
  • So, ([^~]*$)
• If it’s none of the above, we’re “inside”
  • Keep finding the next comma before ~ (so we’re still “inside”)
    • So, ([^,~]*), (don’t capture the comma!)
  • If we find ~ instead of a comma, then go out, then go back in on the next ~
    • So, ([^,~]*~[^~]*~)

In all cases, we make sure we capture enough to reconstruct the string.

References

• regular-expressions.info/Character Classes, Anchors, Grouping and backreferences

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