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Exception in thread “main” java.util.regex.PatternSyntaxException: Illegal/unsupported escape sequence near index 2

I’m trying to remove some words from the line. I don’t want to prescribe them but replace them, because the words that I remove may increase. So I used an array. But when I try to do this, I get errors. I will be glad of any help.

 String[] a = new String[]{
                "\bof \b",
                "\bor \b "," \bit \b "," \bto \b "
        };
        String str = "asdasdas of or asdasd";
        str = str.replaceAll(
                Arrays.toString(a)
                , "");

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Answer

This is a partial answer..

Problem #1: The Arrays.toString(a) returns a string which is bounded by [] so this is the result:

[b of b, bor b ,  bit  b , bto b ]

The brackets are special to regex to define the start-end of a character class definition. b in a character class definition does not mean “word boundary” but rather results in an “illegal escape sequence”.

So first step is to remove the brackets from the regex string (from here).

String regex = Arrays.toString(a).replace("[","").replace("]", "");

Problem #2: Your regex now looks like:

b of b, bor b ,  bit  b , bto b

This is not likely what you want – here’s what I interpret what you want:

Remove all occurrences of of OR or OR it OR to iff surrounded by word boundaries to include removing the trailing space.

(Note also the space after the expressions which should be removed.)

So assume we start with:

String[] a = new String[] { "\bof \b", "\bor \b", " \bit  \b", "\bto \b" };

So to implement the “OR” part you need:

bof b|bor b|bit b|bto b

And so the replace operation would look like:

str = str.replaceAll("\bof \b|\bor \b|\bit \b|\bto \b","");

To continue using your array approach you could then use:

String regex = Arrays.toString(a).replace("[","").replace("]", "");
regex = regex.replaceAll(", +","|");

which yields the regex from your array (same as discussed before):

bof b|bor b|bit  b|bto b

And so

String str = "asdasdas of or asdasd";
str = str.replaceAll(regex,"");

yields:

asdasdas asdasd

I was a bit loose in the treatment of regex explanation so I would invite others to be more precise in their answers.

Good luck.

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