Java trim all whitespace

Java Trim String

In this Java tutorial, you will learn how to trim all white spaces at the beginning and ending of the string using String.trim() method, with examples.

Java Trim String

To trim all white spaces at the beginning and ending of the string, you can use String.trim() function.

trim() function creates and returns a new string with all the leading and trailing space characters.

trim() considers all the unicode characters from ‘\u0000’ to ‘\u0020’ for trimming at the edges of the string. These set of characters contain all the white space characters like single space, thin space, tab, line feed, carriage return etc.

Syntax of trim()

Following is the syntax of trim() function in String class.

Examples

1. Trim whitespaces from edges of a string

In the following Java program, we initialize a String with some white space characters like single space, new line and new tab. We shall then apply the trim() function to this string and observe the output.

Example.java

Run the above program and you shall see something similar to the following in console window.

"Hello World! Welcome to www.tutorialkart.com"

We have just added leading and trailing double quotes to understand the extent of the resulting string.

The leading and trailing white spaces are gone in the resulting string from trim() function.

Also, note that the white space characters inside the string are preserved. Like the white spaces and new line in this example.

2. Trim String where the string has only whitespace characters in it

In the following Java program, we initialize a String with only white space characters and nothing else.

Example.java

/** * Java Example Program to Trim white space characters at the edges of string */ public class Example < public static void main(String[] args) < //initialize string String str = " \t \n \n\t \n \n \t \r \f \n"; //trim string String result = str.trim(); System.out.print("\""+result+"\""); >>

Run the above program, and you shall get the following in the console output.

The resulting String is just an empty string, since there are no characters with unicode greater than ‘\u0020’.

Conclusion

In this Java Tutorial, we learned how to trim white spaces in a string at the leading and trailing edges.

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Remove Whitespace From String in Java

In Java, removing whitespace from a String is a common need when manipulating strings. This article will discuss eliminating all or a portion of the existing whitespace in the string. We’ll look at numerous built-in Java ways to accomplish the same thing. Let’s explore common scenarios of removing whitespace from a String in Java.

Introduction

Suppose you have to display a list of strings, but each of these strings has some spaces at the end, added mistakenly. This needs to be removed before displaying. Likewise, there can be spaces in between or at the beginning of the strings.

We shall be looking at Java programs to remove these spaces. Also, Java provides numerous in-built methods to perform this task. To list a few:

• trim() : It removes the leading and trailing spaces present in the string. You can see this in the image below:
• strip() : It removes the leading and trailing spaces present in the string. Also, it is Uniset/Unicode character aware. We shall learn more about it in a section ahead.
• stripLeading() : It removes the spaces present at the beginning of the string.
• stripTrailing() : It removes the spaces present at the end of the string.
• replaceAll() : It replaces all the matched substrings with a new string. We shall be discussing the methods along with the implementation ahead.

trim() method in Java

This is the most common method to remove white spaces present at the beginning and end of the string. For trim() method, space character is a character having ASCII values

Signature: trim() method is defined as:

Syntax: trim() method is written as

Parameters: trim() method takes no parameters.

Return Values: It returns the modified version of the original string, with no spaces at the end and beginning.

Exceptions: It throws

Explanation: In the above program, the value of the string is null; hence exception is thrown.

Let us look at the correct implementation. Program to Remove Leading and Trailing Whitespaces

Explanation:
The trim() method is used in the program above to trim the strings s and s1 . In contrast to s1 , which contains numerous spaces, s only has one space at the beginning and one at the end. These spaces are eliminated once the method trim() is called and the output is printed.

strip() method Java 11

The strip() method was introduced in Java 11. It also removes leading and trailing spaces present in the string. But that is exactly what trim() does. What’s the difference between the two?

strip() method is Unicode aware, a modification over trim() .The reason behind the addition of this method is that there exist numerous space characters as per the Unicode standards having ASCII value > 32(‘U+0020’); the strip() method can remove them as well.

trim()	strip()
It was introduced in Java 1.	It was introduced in Java 11.
It makes use of ASCII values.	It makes use of the Unicode value.
It removes space characters with ASCII values less than or equal to 32(‘U+0020’)	It removes all the space characters as per the Unicode standards having ASCII value greater than 32(‘U+0020’)

Signature: strip() method is defined as:

Syntax: strip() method is written as

Parameters: strip() method takes no parameters.

Return Values: It returns the modified version of the original string, i.e., with no spaces at the end and beginning.

Exceptions: It throws

Explanation: In the above program, the value of the string is null; hence exception is thrown.

Let us look at the correct implementation and understand the difference between the two. Program to Remove Leading and Trailing Whitespaces

Explanation:
In the above program, we have appended a whitespace character with ASCII value: ‘U + 2003’. So as you can see, the trim() method does not remove it as the value is not less than ‘U+0020’. Whereas in the case of strip() , it gets removed. This pretty much explains the advantage of strip() over trim() .

stripLeading() method Java 11

stripLeading() method removes all the leading spaces or the spaces present at the beginning of the string. It was introduced in Java 11. Just like strip() , it can remove the space characters space characters as per the Unicode standards having ASCII value greater than 32(‘U+0020’).

Signature: stripLeading() method is defined as:

Syntax: stripLeading() method is written as

Parameters: stripLeading() method takes no parameters.

Return Values: It returns the modified version of the original string, i.e., with no spaces at the beginning. Exceptions: It throws

Explanation: In the above program, the value of the string is null; hence exception is thrown.

Below is the correct implementation:
Program to Remove Leading Whitespaces

Explanation:
In the above program, the stripLeading() method is called on two strings. One of these has a space character with a codepoint value > 32(‘U+0020’). As you can see, in both cases, the spaces present at the beginning get removed; however, the ones at the end are still present.

stripTrailing() method Java 11

This method is exactly the opposite of the stripLeading() method. It removes all the trailing or the spaces present at the end of the string. It was also introduced in Java11. See the image below for reference: Signature: stripTrailing() method is defined as:

Syntax: stripTrailing() method is written as

Parameters: stripTrailing method takes no parameters.

Return Values: It returns the modified string with no spaces at the end.

Exceptions: It throws

Explanation:
In the above program, the value of the string is null; hence exception is thrown.
Below is the correct implementation.
Program to Remove Trailing Whitespaces

Explanation: In the above program stripLeading() method is called on two strings. One of these has a space character with a codepoint value > 32(‘U+0020’). As you can see, in both cases, the spaces present at the end get removed. However, the ones at the beginning are still present.

replaceAll(String regex, String replacement)

replaceAll() is a very commonly used method for string manipulation in Java. This method replaces all the substrings of the string matching the specified regex expression with the specified replacement text.

A regular expression or regex is a string pattern that we use for some searching or matching kind of operations.

We can use this method to remove spaces from the string. All we need to do is specify the regex expression for the kind of spaces that need to be removed, i.e., trailing or leading, or both. The following table shows the regex expressions for the same:

Signature: replaceAll() method is defined as:

Syntax: replaceAll() method is written as

Parameters: replaceAll method takes two parameters:

• String regex : The regular expression that is used for matching the substring.
• String replacement : The string that replaces the matched substring.

Return Values: It returns the modified string, where all the occurrences of matched substrings are replaced by the string specified as a parameter. Exceptions: It throws :

Explanation: So in the above program, the syntax defined for regex is incorrect; hence exception is thrown.

Program to Remove All Whitespaces and Leading, Trailing Whitespaces

Explanation In the above program, replaceAll() is called with different regular expressions as parameters to remove leading, trailing, and all the spaces.

Note: We can not directly use «» in Java, escape character is required. Thus, «\» is used instead.

Conclusion

• Java has inbuilt methods to remove the whitespaces from the string, whether leading, trailing, both, or all.
• trim() method removes the leading and trailing spaces present in the string.
• strip() method removes the leading and trailing spaces present in the string. Also, it is Uniset/Unicode character aware.
• stripleading() method removes the spaces present at the beginning of the string.
• striptrailing() method removes the spaces present at the end of the string.
• replaceall(String regex, String replacement) method replaces all the matched substring with a new string.

Источник

Java Guides

In this short article, we look at how to remove or trim all white spaces from a given string in Java.

Let’s first we’ll write Java method to trim all whitespace from the given String that is trim white spaces from leading, trailing, and in between characters.

trimAllWhitespace(String str) Method

Logical steps

1. Iterate over each character of a given String.
2. Check each character with white space using built-in Character.isWhitespace(c) method.
3. If the character is not a white space then append a character to StringBuilder instance.
4. Finally, return String via calling toString() method on StringBuilder instance.

/** * Trim i>all whitespace from the given @code String>: * leading, trailing, and in between characters. * @param str the @code String> to check * @return the trimmed @code String> * @see java.lang.Character#isWhitespace */ public static String trimAllWhitespace(String str) < if (!hasLength(str)) < return str; > int len = str.length(); StringBuilder sb = new StringBuilder(str.length()); for (int i = 0; i  len; i++) < char c = str.charAt(i); if (!Character.isWhitespace(c)) < sb.append(c); > > return sb.toString(); >

Complete Java Program

package com.javaguides.corejava.string; /** * @author Ramesh Fadatare * */ public class StringTrimAllWhitespace < public static void main(String[] args) < String str = " Java Guides "; String result = trimAllWhitespace(str); System.out.println(result); > /** * Trim i>all whitespace from the given @code String>: * leading, trailing, and in between characters. * @param str the @code String> to check * @return the trimmed @code String> * @see java.lang.Character#isWhitespace */ public static String trimAllWhitespace(String str) < if (!hasLength(str)) < return str; > int len = str.length(); StringBuilder sb = new StringBuilder(str.length()); for (int i = 0; i  len; i++) < char c = str.charAt(i); if (!Character.isWhitespace(c)) < sb.append(c); > > return sb.toString(); > public static boolean hasLength(String str) < return (str != null && !str.isEmpty()); > >

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