How to remove newlines from beginning and end of a

问题:

I have a string that contains some text followed by a blank line. What's the best way to keep the part with text, but remove the whitespace newline from the end?

回答1:

Use String.trim() method to get rid of whitespaces (spaces, new lines etc.) from the beginning and end of the string.

String trimmedString = myString.trim();

回答2:

String.replaceAll("[\n\r]", "");

回答3:

If your string is potentially null, consider using StringUtils.trim() - the null-safe version of String.trim().

回答4:

String trimStartEnd = "\n TestString1 linebreak1\nlinebreak2\nlinebreak3\n TestString2 \n";
System.out.println("Original String : [" + trimStartEnd + "]");
System.out.println("-----------------------------");
System.out.println("Result String : [" + trimStartEnd.replaceAll("^(\\r\\n|[\\n\\x0B\\x0C\\r\\u0085\\u2028\\u2029])|(\\r\\n|[\\n\\x0B\\x0C\\r\\u0085\\u2028\\u2029])$", "") + "]");

1. Start of a string = ^ ,
2. End of a string = $ ,
3. regex combination = | ,
4. Linebreak = \r\n|[\n\x0B\x0C\r\u0085\u2028\u2029]

回答5:

I'm going to add an answer to this as well because, while I had the same question, the provided answer did not suffice. Given some thought, I realized that this can be done very easily with a regular expression.

To remove newlines from the beginning:

// Trim left
String[] a = "\n\nfrom the beginning\n\n".split("^\\n+", 2);

System.out.println("-" + (a.length > 1 ? a[1] : a[0]) + "-");

and end of a string:

// Trim right
String z = "\n\nfrom the end\n\n";

System.out.println("-" + z.split("\\n+$", 2)[0] + "-");

I'm certain that this is not the most performance efficient way of trimming a string. But it does appear to be the cleanest and simplest way to inline such an operation.

Note that the same method can be done to trim any variation and combination of characters from either end as it's a simple regex.

回答6:

String text = readFileAsString("textfile.txt");
text = text.replace("\n", "").replace("\r", "");