BAEL-5277 generate string of repeated characters (#11611)

* BAEL-5277 generate string of repeated characters

* BAEL-5277 fixed test

* BAEL-5277 fixing tests

* removed public from class and methods, removed unnecessary test examples, extracted contants

* renamed constants

* renamed a test

* fixed the string repeat test

* removed public from class and method

* modified the test

* reset the java version

* tests added

* added apache dependency

* removed repeat method for string

* updated tests

* fixed tests

* added two additional tests

* formatted code

* renaming variables

* 1.0.0 | FIX removed unnecessary annotation

* removing EMPTY_STRING constant

Co-authored-by: Matea Pejčinović <matea.pejcinovic@intellexi.hr>

core-java-modules/core-java-string-algorithms-3/pom.xml

@@ -24,6 +24,11 @@
             <artifactId>commons-validator</artifactId>
             <version>${validator.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${apache-commons-lang3.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -51,6 +56,7 @@
     <properties>
         <guava.version>31.0.1-jre</guava.version>
         <validator.version>1.7</validator.version>
+        <apache-commons-lang3.version>3.12.0</apache-commons-lang3.version>
     </properties>
 
 </project>

core-java-modules/core-java-string-algorithms-3/src/test/java/com/baeldung/repeatedcharstring/RepeatedCharacterStringUnitTest.java

@@ -0,0 +1,92 @@
+package com.baeldung.repeatedcharstring;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.stream.Collectors;
+
+import com.google.common.base.Joiner;
+import com.google.common.base.Strings;
+
+import static java.util.stream.Stream.generate;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class RepeatedCharacterStringUnitTest {
+
+    private static final String EXPECTED_STRING = "aaaaaaa";
+    private static final int N = 7;
+
+    @Test
+    void givenString_whenStringBuilderUsed_thenStringCreated() {
+        StringBuilder builder = new StringBuilder(N);
+        for (int i = 0; i < N; i++) {
+            builder.append("a");
+        }
+        String newString = builder.toString();
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenCharArrayUsed_thenStringCreated() {
+        char[] charArray = new char[N];
+        for (int i = 0; i < N; i++) {
+            charArray[i] = 'a';
+        }
+        String newString = new String(charArray);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenApacheStringUtilsUsed_thenStringCreated() {
+        char charToAppend = 'a';
+        String newString = StringUtils.repeat(charToAppend, N);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenGuavaRepeatUsed_thenStringCreated() {
+        String charToAppend = "a";
+        String newString = Strings.repeat(charToAppend, N);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenArraysFillUsed_thenStringCreated() {
+        char charToAppend = 'a';
+        char[] charArray = new char[N];
+        Arrays.fill(charArray, charToAppend);
+        String newString = new String(charArray);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenGenerateAndJoiningUsed_thenStringCreated() {
+        String charToAppend = "a";
+        String newString = generate(() -> charToAppend).limit(N).collect(Collectors.joining());
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenStringJoinUsed_thenStringCreated() {
+        String charToAppend = "a";
+        String newString = String.join("", Collections.nCopies(N, charToAppend));
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenGuavaJoinerUsed_thenStringCreated() {
+        String charToAppend = "a";
+        String newString = Joiner.on("").join(Collections.nCopies(N, charToAppend));
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenString_whenRandomStringUtilsUsed_thenStringCreated() {
+        String charToAppend = "a";
+        String newString = RandomStringUtils.random(N, charToAppend);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+}