7 ways to remove spaces from String!

This article was reproduced from the public number: Hollis

Strings are one of the most commonly used data types in Java. W e often use strings to do a lot of things in our daily development. Such as string stitching, truncation, replacement, etc.

In this article, we describe one of the more common and easy-to-ignore operations to remove spaces from strings.

In fact, there are many different ways to remove spaces from strings in Java, such as trim replaceAll and so on. However, some new features have been added to Java 11, such as strip stripLeading stripTrailing and so on.

Most of the time, we just use trim method to remove extra spaces. But as if a lot of people hadn't thought about it, is there a better way?

Of course, trim() works well in most cases, but there are many different approaches in Java. E ach has its own advantages and disadvantages. How do we decide which method is best for us?

Next we'll look at a few methods and compare their differences and strengths and weaknesses.

Different ways to remove spaces from a string in java

First, let's look at how many methods to remove the space section from String and the author summarizes the following 7 (JDK native comes with a method that does not include similar methods in the third-party tool class library):

• trim(): Removes spaces at the beginning and end of the string.
• Strip(): Removes spaces at the beginning and end of the string.
• StripLeading(): Removes only spaces at the beginning of the string
• StripTrailing(): Only spaces at the end of the string are removed
• replace(): Replace all target characters with new characters
• replaceAll(): Replace all matching characters with new characters. This method uses regular expressions as input to identify the target substrings that need to be replaced
• replaceFirst(): Replaces only the character that first appears as the target substring with the new string

The most important thing to note is that String objects are immutable in Java, which means we can't modify strings, so all of the above methods we get is a new string.

Next, we learn the usage for each of these methods and understand its characteristics.

PS: This article code is done using the online run tool (www.jdoodle.com/online-java-compiler/) because my tester does not have Java 11 installed and Unicode characters are incomplete. If you also want to experiment, it is recommended to use the online tool, select the corresponding JDK.

trim

trim() is the most common way for Java developers to remove spaces at the beginning and end of strings. The usage is also relatively simple:

public class StringTest {


    public static void main(String[] args) {


        String stringWithSpace = "   Hollis   Is   A   Java   Coder   ";


        StringTest.trimTest(stringWithSpace);


    }


    private static void trimTest(String stringWithSpace){


        System.out.println("Before trim : \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.trim();


        System.out.println("After trim : \'" + stringAfterTrim + "\'");


    }


}

Output:

Before trim : '   Hollis   Is   A   Java   Coder   '


After trim : 'Hollis   Is   A   Java   Coder'

As above, after using trim the space content at the beginning and end of the original string is removed.

But I don't know if you've ever thought about what the white space removed by the trim method contains? Are there any other characters besides spaces?

In fact, the blank character removed by trim refers to any character whose ASCII value is less than or equal to 32 ('U'0020'):

It contains characters such as spaces, line breaks, backstags, and so on.

strip()

I wonder if you've noticed that in the release of Java 11, a new strip() method has been added to remove leading and ending spaces from the string.

Now that you have a trim method, why add a strip

This is actually because trim method can only remove characters with ASCII values less than or equal to 32, but according to Unicode, there are many other blank characters besides characters in ASCII.

And to recognize these space characters, a new isWhitespace(int) method has been added to the Character class, starting with Java 1.5. T his method uses unicode to identify space characters. You can learn more unicode space characters in jkorpela.fi/chars/spaces.html.

The new strip method in Java 11 is to use this Character.isWhitespace(int) method to determine if they are blank characters and remove them:

Let's look at an example of using strip:

public class StringTest {


    public static void main(String args[]) {


      String stringWithSpace ='\u2001' + "  Hollis   Is   A   Java   Coder  " + '\u2001';


        System.out.println("'" + '\u2001' + "' is space : " +  Character.isWhitespace('\u2001'));


        StringTest.stripTest(stringWithSpace);


    }


    private static void stripTest(String stringWithSpace){


        System.out.println("Before strip : \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.strip();


        System.out.println("After strip : \'" + stringAfterTrim + "\'");


    }


}

We've added a special character before and after the string, \u2001 is not in ASCII and is judged by Character.isWhitespace to be a blank character. The strip is then used for processing, and the output is as follows:

' ' is space : true


Before strip : '   Hollis   Is   A   Java   Coder   '


After strip : 'Hollis   Is   A   Java   Coder'

Therefore, the strip method in Java 11 is more powerful than the trim method, which removes many blank characters that are not in ASCII and is judged by the Acter.isWhitespace method.

The difference between the trim and strip methods

Above we describe two ways to remove the beginning and end of a string, trim and strip and compare their differences:

StripLeading() and StripTrailing()

The stripLeading() and stripTrailing () methods were also added in Java 11. The effect is to remove the space at the beginning of the string and the space at the end of the string.

Similar to strip method, stripLeading stripTrailing also uses Character.isWhitespace(int) to identify blank characters. The usage is similar to strip

public class StringTest {


    public static void main(String args[]) {


      String stringWithSpace ='\u2001' + "  Hollis   Is   A   Java   Coder  " + '\u2001';


        System.out.println("'" + '\u2001' + "' is space : " +  Character.isWhitespace('\u2001'));


        StringTest.stripLeadingTest(stringWithSpace);


        StringTest.stripTrailingTest(stringWithSpace);


    }




    private static void stripLeadingTest(String stringWithSpace){


        System.out.println("Before stripLeading : \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.stripLeading();


        System.out.println("After stripLeading : \'" + stringAfterTrim + "\'");


    }




     private static void stripTrailingTest(String stringWithSpace){


        System.out.println("Before stripTrailing : \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.stripTrailing();


        System.out.println("After stripTrailing : \'" + stringAfterTrim + "\'");


    }


}

Output:

' ' is space : true


Before stripLeading : '   Hollis   Is   A   Java   Coder   '


After stripLeading : 'Hollis   Is   A   Java   Coder   '


Before stripTrailing : '   Hollis   Is   A   Java   Coder   '


After stripTrailing : '   Hollis   Is   A   Java   Coder'

replace

In addition to using trim and strip there is another way to remove white space characters from strings, which is to replace them with replace method.

Replace is added from java 1.5 and can replace each target substring with the specified string.

This method replaces all matching target elements as follows:

 public class StringTest {


    public static void main(String args[]) {


        String stringWithSpace ="  Hollis   Is   A   Java   Coder  ";


        StringTest.replaceTest(stringWithSpace);


    }






    private static void replaceTest(String stringWithSpace){


        System.out.println("Before replace : \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.replace(" ", "");


        System.out.println("After replace : \'" + stringAfterTrim + "\'");


    }


}

outcome:

Before replace : '  Hollis   Is   A   Java   Coder  '


After replace : 'HollisIsAJavaCoder'

As you can see, the above use replace method can replace all the blank characters in the string. II.

replaceAll

replaceAll is one of the most powerful string manipulation methods added in Java 1.4. We can use this approach for many purposes.

Using replaceAll() method, we can use regular expressions to identify the content of the target character that needs to be replaced. With regular expressions, you can do many things, such as deleting all spaces, removing opening spaces, deleting end spaces, and so on.

We just need to create the correct regular expression with the correct replacement parameters. Some examples of regular expressions are:

\s+   所有的空白字符


^\s+      字符串开头的所有空白字符


\s+$      字符串结尾的所有空白字符

Note that to add/we have to use escape \s+ in java we have to \\s+

public class StringTest {


    public static void main(String args[]) {


        String stringWithSpace ="  Hollis   Is   A   Java   Coder  ";


        StringTest.replaceAllTest(stringWithSpace," ");


        StringTest.replaceAllTest(stringWithSpace,"\\s+");


        StringTest.replaceAllTest(stringWithSpace,"^\\s+");


        StringTest.replaceAllTest(stringWithSpace,"\\s+$");


    }




    private static void replaceAllTest(String stringWithSpace,String regex){


        System.out.println("Before replaceAll with '"+ regex +"': \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.replaceAll(regex, "");


        System.out.println("After replaceAll with '"+ regex +"': \'" + stringAfterTrim + "\'");


    }


}

outcome:

Before replaceAll with ' ': '  Hollis   Is   A   Java   Coder  '


After replaceAll with ' ': 'HollisIsAJavaCoder'


Before replaceAll with '\s+': '  Hollis   Is   A   Java   Coder  '


After replaceAll with '\s+': 'HollisIsAJavaCoder'


Before replaceAll with '^\s+': '  Hollis   Is   A   Java   Coder  '


After replaceAll with '^\s+': 'Hollis   Is   A   Java   Coder  '


Before replaceAll with '\s+$': '  Hollis   Is   A   Java   Coder  '


After replaceAll with '\s+$': '  Hollis   Is   A   Java   Coder'

As we can see, if you use replaceAll() with the appropriate regular expression, it will be a very powerful method.

replaceFirst

replaceFirst method was also added in java 1.4, which replaces only the first match of a given regular expression with a replacement string.

This method is useful if you only need to replace the first occurrence. For example, if we just need to remove ^\\s+ the leading \\s+ we can use the .

We can also use this method to remove the end space by \\s+ the regular expression of . B ecause this expression will only match the last space of the row. So the last space is considered the first match for this method.

Let's give an example of removing leading and trailing spaces from a string

public class StringTest {


    public static void main(String args[]) {


        String stringWithSpace ="  Hollis   Is   A   Java   Coder  ";


        StringTest.replaceFirstTest(stringWithSpace," ");


        StringTest.replaceFirstTest(stringWithSpace,"\\s+");


        StringTest.replaceFirstTest(stringWithSpace,"^\\s+");


        StringTest.replaceFirstTest(stringWithSpace,"\\s+$");


    }




    private static void replaceFirstTest(String stringWithSpace,String regex){


        System.out.println("Before replaceFirst with '"+ regex +"': \'" + stringWithSpace + "\'");


        String stringAfterTrim = stringWithSpace.replaceFirst(regex, "");


        System.out.println("After replaceFirst with '"+ regex +"': \'" + stringAfterTrim + "\'");


    }


}

outcome:

Before replaceFirst with ' ': '  Hollis   Is   A   Java   Coder  '


After replaceFirst with ' ': ' Hollis   Is   A   Java   Coder  '


Before replaceFirst with '\s+': '  Hollis   Is   A   Java   Coder  '


After replaceFirst with '\s+': 'Hollis   Is   A   Java   Coder  '


Before replaceFirst with '^\s+': '  Hollis   Is   A   Java   Coder  '


After replaceFirst with '^\s+': 'Hollis   Is   A   Java   Coder  '


Before replaceFirst with '\s+$': '  Hollis   Is   A   Java   Coder  '


After replaceFirst with '\s+$': '  Hollis   Is   A   Java   Coder'

summary

This article describes seven ways to remove blank characters from a string.

To remove the blank characters at the beginning of the string directly, you can use stripLeading replaceAll and replaceFirst

To remove white space characters directly from the end of a string, you can use stripTrailing replaceAll and replaceFirst

To remove both blank characters at the beginning and end of a string, you can use strip trim

To remove all blank characters from a string, you can use replace and replaceAll

Java's 11 new strip stripTrailing and stripLeading methods can remove more characters than any other method, and the white space characters he can remove are not limited to characters in ASCII but all blank characters in Unicode as can be judged by Character.isWhitespace

Here are 7 ways W3Cschool编程狮 can remove spaces from String! Related to the introduction, I hope to help you.