How Can I Remove Multiple Spaces and Leading/Trailing Whitespace in Java?

Removing Multiple Spaces and Leading/Trailing Whitespace in Java

When working with strings in Java, it's often necessary to manipulate whitespace to improve readability and consistency. One common task is replacing multiple spaces with a single space while also removing spaces at the beginning and end of a string.

Let's start with a classic example: converting " hello there " to "hello there."

Using trim() and replaceAll()

A straightforward approach involves combining the trim() and replaceAll() methods:

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

The trim() method removes all leading and trailing whitespace, while replaceAll() replaces multiple consecutive spaces (" ") with a single space.

Regex-Only Solution

It's also possible to accomplish this with a single replaceAll using regular expressions:

String result = before.replaceAll("^ +| +$|( )+", "");

This regex has three alternate patterns:

• "^ ": Matches any sequence of spaces at the beginning of the string
• " $": Matches any sequence of spaces at the end of the string
• "( ) ": Matches any sequence of spaces that matches neither of the above (i.e., multiple spaces in the middle)

For each pattern, $1 captures the empty string (for leading/trailing spaces) or a single space (for multiple spaces in the middle).

See Also

• String.trim() for more information on removing whitespace
• regular-expressions.info/Repetition for details on regex repetition patterns
• regular-expressions.info/Anchors for information on regex anchors

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