Remove Non-alphabetic Characters From String Array Example

Mary ZhengDecember 30th, 2024Last Updated: December 23rd, 2024

0 177 2 minutes read

1. Introduction

Removing non-alphabetic characters from a string is useful for an application that includes text search, match, and analysis. In this example, I will show four ways to remove non-alphabetic characters string:

via String.replaceAll method with regular expressions.
via character filtering with java.util.Stream.
via StringBuilder from the java.lang package to append the alphabetic characters.
via RegExUtils.replaceAll from Apache Commons Lang.

2. Setup

In this step, I will create a maven project with both Apache Commons Lang and Junit 5 libraries.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>org.zheng</groupId>
    <artifactId>t</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <dependencies>
 
        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.17.0</version>
        </dependency>
 
        <!--
        https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-api -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.11.4</version>
            <scope>test</scope>
        </dependency>
 
    </dependencies>
 
</project>

3. Remove All Non-alphabetic Characters String

In this step, I will create a RemoveNonAlphabeticUtil.java class that includes four methods to remove non-alphabetic characters.

viaCharacter utilizes the StringBuilder to append the alphabetic characters from the character in toCharArray.
viaRegExUtils_replaceAll uses the replaceAll method from org.apache.commons.lang3.RegExUtils.
viaString_replaceAll_RegEx uses the replaceAll method from java.lang.String.
viaStream filters out any non-alphabetic character.

RemoveNonAlphabeticUtil.java

package org.zheng.demo;
 
import java.util.Arrays;
 
import org.apache.commons.lang3.RegExUtils;
 
public class RemoveNonAlphabeticUtil {
    private static final String NON_ALPHA_REGEX = "[^a-zZ-Z]";
 
    public String viaCharacter(final String testStr) {
        StringBuilder sb = new StringBuilder();
        for (char c : testStr.toCharArray()) {
            if (Character.isLetter(c)) {
                sb.append(c);
            }
        }
        return sb.toString();
    }
 
    public String viaRegExUtils_replaceAll(final String testMsgs) {
        return RegExUtils.replaceAll(testMsgs, NON_ALPHA_REGEX, "");
 
    }
 
    public String viaString_replaceAll_RegEx(final String testMsgs) {
        return testMsgs.replaceAll(NON_ALPHA_REGEX, "");
 
    }
 
    public String[] viaStream(final String[] stringArray) {
        return Arrays.stream(stringArray)
                .map(str -> str.chars().filter(Character::isLetter)
                        .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append).toString())
                .toArray(String[]::new);
 
    }
 
}

Line 8: the regular expression [^a-zA-Z] matches any non-alphabetic character, meaning any character that is neither a lowercase nor an uppercase letter.
Line 13: append only if the Character.isLetter(c) is true.
Line 21: replace any non-alphabetic character with “” via the org.apache.commons.lang3.RegExUtils.replaceAll method.
Line 26: replace any non-alphabetic character with “” via the java.lang.String.replaceAll method.
Line 32: remove any non-alphabetic character with Character::isLetter via the java.util.Stream.filter method.

4. Junit Test

In this step, I will create a RemoveNonAlphabeticUtilTest.java to test the four methods defined in step 3.

RemoveNonAlphabeticUtilTest.java

package org.zheng.demo;
 
import static org.junit.jupiter.api.Assertions.assertEquals;
 
import org.junit.jupiter.api.Test;
 
class RemoveNonAlphabeticUtilTest {
 
    String[] stringArray = { "this ", "is:", "some odd!~12323", "characters!" };
 
    RemoveNonAlphabeticUtil testClass = new RemoveNonAlphabeticUtil();
 
    @Test
    void test_viaCharacter() {
        for (int idx = 0; idx < stringArray.length; idx++) {
            stringArray[idx] = testClass.viaCharacter(stringArray[idx]);
        }
 
        verifyData(stringArray);
    }
 
    @Test
    void test_viaRegExUtils_replaceAll() {
        for (int idx = 0; idx < stringArray.length; idx++) {
            stringArray[idx] = testClass.viaRegExUtils_replaceAll(stringArray[idx]);
        }
 
        verifyData(stringArray);
    }
 
    @Test
    void test_viaString_replaceAll_RegEx() {
        for (int idx = 0; idx < stringArray.length; idx++) {
            stringArray[idx] = testClass.viaString_replaceAll_RegEx(stringArray[idx]);
        }
 
        verifyData(stringArray);
    }
 
    @Test
    void test_viaStream() {
        String[] updatedStrs = testClass.viaStream(stringArray);
 
        verifyData(updatedStrs);
    }
 
    private void verifyData(final String[] stringArray) {
        assertEquals("this", stringArray[0]);
        assertEquals("is", stringArray[1]);
        assertEquals("someodd", stringArray[2]);
        assertEquals("characters", stringArray[3]);
    }
}

Line 9: defines a test string array { “this “, “is:”, “some odd!~12323”, “characters!” }. Note: there are some non-alphabetic characters: white space, colon(:), exclamation mark(!), tilde(~), and numeric digits(12323).
Line 48: verifies that the white space is removed.
Line 49: verifies that the colon is removed.
Line 50: verifies that the white space, “!”, “~“, and digits are removed.
Line 51: verifies that the “!” is removed.

5. Demonstration

In this step, I will run the Junit tests and capture the test results.

remove non alphabetic characters string — Figure 1 Test Results

6. Conclusion

In this example, I created a simple maven project that included a Java class with four methods to remove non-alphabetic characters from a string. Both viaString_replaceAll_RegEx and viaRegExUtils_replaceAll methods utilize replaceAll with a regular expression argument from both org.apache.commons.lang3.RegExUtils and java.lang.String classes.

7. Download

This was an example of a maven project which removed non-alphabetic characters from a string.

Download
You can download the full source code of this example here: Remove Non-alphabetic Characters From String Array Example

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Remove Non-alphabetic Characters From String Array Example

1. Introduction

2. Setup

3. Remove All Non-alphabetic Characters String

4. Junit Test

5. Demonstration

6. Conclusion

7. Download

Thank you!

Mary Zheng

Thank you!

1. Introduction

2. Setup

3. Remove All Non-alphabetic Characters String

4. Junit Test

5. Demonstration

6. Conclusion

7. Download

Thank you!

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