How to Efficiently Remove Multiple Spaces from a Java String?

How to Remove Multiple Spaces from a String in Java

In Java, a common task is to clean up strings by removing extra spaces and leading or trailing whitespaces. Here's how to achieve this:

To replace multiple consecutive spaces with a single space, use the replaceAll method with a regular expression:

String mytext = " hello     there   ";
mytext = mytext.replaceAll(" +", " ");

This regex matches one or more consecutive spaces ( ) and replaces them with a single space.

To remove leading and trailing spaces while also collapsing multiple spaces, use trim and replaceAll in combination:

String after = before.trim().replaceAll(" +", " ");

trim removes spaces at the beginning and end of the string, and replaceAll replaces multiple spaces within the string with a single space.

For more control over matching and replacing whitespace, consider using anchors and capturing groups in the provided regex example:

String[] tests = {
    "  x  ",
    "  1   2   3  ",
    "",
    "   ",
};
for (String test : tests) {
    System.out.format("[%s]%n",
        test.replaceAll("^ +| +$|( )+", "")
    );
}

This regex is more complex but allows for precise matching and replacement of whitespace.

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