BAEL-5614 Remove Last Char from String Builder (#12577)

* BAEL-5614 Remove Last Char from String Builder
- Added initial code with main
- Added initial tests for each method going to be written on

* Update RemoveLastChar.java

* Update and rename RemoveLastCharTest.java to RemoveLastCharUnitTest.java

Co-authored-by: Grzegorz Piwowarek <gpiwowarek@gmail.com>

core-java-modules/core-java-string-operations-4/src/main/java/com/baeldung/stringbuilder/RemoveLastChar.java

@@ -0,0 +1,67 @@
+package com.baeldung.stringbuilder;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.List;
+import java.util.StringJoiner;
+
+public class RemoveLastChar {
+    static List<String> technologies = List.of("Spring Boot", "Quarkus", "Micronaut");
+
+    public static StringBuilder joinStringsWithLastCharAsDelimiter() {
+        StringBuilder sb = new StringBuilder();
+
+        for (String tech : technologies) {
+            sb.append(tech)
+                .append(",");
+        }
+
+        return sb;
+    }
+
+    public static StringBuilder removeLastCharWithDeleteLastChar(StringBuilder sb) {
+
+        if (sb.length() == 0) {
+            return sb;
+        }
+
+        return sb.deleteCharAt(sb.length() - 1);
+    }
+
+    public static StringBuilder removeLastCharWithSetLength(StringBuilder sb) {
+
+        if (sb.length() == 0) {
+            return sb;
+        }
+
+        sb.setLength(sb.length() - 1);
+        return sb;
+    }
+
+    public static StringBuilder joinStringsWithoutLastCharAsDelimiter() {
+        StringBuilder sb = new StringBuilder();
+        String prefix = "";
+
+        for (String tech : technologies) {
+            sb.append(prefix);
+            prefix = ",";
+            sb.append(tech);
+        }
+
+        return sb;
+    }
+
+    public static String joinStringsUsingJoin() {
+        return String.join(",", technologies);
+    }
+
+    public static String joinUsingStringJoiner() {
+        StringJoiner joiner = new StringJoiner(",");
+        technologies.forEach(joiner::add);
+        return joiner.toString();
+    }
+
+    public static String joinUsingStringUtils() {
+        return StringUtils.join(technologies, ",");
+    }
+}

core-java-modules/core-java-string-operations-4/src/test/java/com/baeldung/stringbuilder/RemoveLastCharUnitTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.stringbuilder;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.Assert;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class RemoveLastCharUnitTest {
+
+    private static final String STRING_WITH_CHAR = "Spring Boot,Quarkus,Micronaut,";
+    private static final String STRING_WITHOUT_CHAR = "Spring Boot,Quarkus,Micronaut";
+
+    @Test
+    void givenCharAtEndOfString_whenRemoveLastCharWithDeleteLastChar_thenLastCharRemoved() {
+        StringBuilder sb = RemoveLastChar.joinStringsWithLastCharAsDelimiter();
+        Assertions.assertEquals(STRING_WITH_CHAR, sb.toString());
+
+        RemoveLastChar.removeLastCharWithDeleteLastChar(sb);
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, sb.toString());
+    }
+
+    @Test
+    void givenCharAtEndOfString_whenRemoveLastCharWithSetLength_thenLastCharRemoved() {
+        StringBuilder sb = RemoveLastChar.joinStringsWithLastCharAsDelimiter();
+        Assertions.assertEquals(STRING_WITH_CHAR, sb.toString());
+
+        RemoveLastChar.removeLastCharWithSetLength(sb);
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, sb.toString());
+    }
+
+    @Test
+    void whenForLoopJoinWithPrefix_thenLastCharIsNotPresent() {
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, RemoveLastChar.joinStringsWithoutLastCharAsDelimiter()
+            .toString());
+    }
+
+    @Test
+    void whenJoiningStringsUsingJoin_thenLastCharIsNotPresent() {
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, RemoveLastChar.joinStringsUsingJoin());
+    }
+
+    @Test
+    void whenJoiningStringsUsingStringJoiner_thenLastCharIsNotPresent() {
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, RemoveLastChar.joinUsingStringJoiner());
+    }
+
+    @Test
+    void whenJoiningStringsUsingStringUtils_thenLastCharIsNotPresent() {
+        Assertions.assertEquals(STRING_WITHOUT_CHAR, RemoveLastChar.joinUsingStringUtils());
+    }
+}