This commit is related to BAEL-7858 (#16507)

This commit aims to add a test class "RemoveAllCharsBeforeSpecificOneUnitTest".

core-java-modules/core-java-string-operations-9/src/test/java/com/baeldung/removeallcharsbeforechar/RemoveAllCharsBeforeSpecificOneUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.removeallcharsbeforechar;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class RemoveAllCharsBeforeSpecificOneUnitTest {
+    String inputString = "Hello World!";
+    char targetCharacter = 'W';
+
+    @Test
+    public void givenString_whenUsingSubstring_thenCharactersRemoved() {
+        String result = inputString.substring(inputString.indexOf(targetCharacter));
+        assertEquals("World!", result);
+    }
+
+    @Test
+    public void givenString_whenUsingRegex_thenCharactersRemoved() {
+        String result = (targetCharacter) + inputString.replaceAll(".*" + targetCharacter, "");
+        assertEquals("World!", result);
+    }
+
+    @Test
+    public void givenString_whenUsingStringBuilder_thenCharactersRemoved() {
+        StringBuilder sb = new StringBuilder(inputString);
+        int index = sb.indexOf(String.valueOf(targetCharacter));
+        if (index != -1) {
+            sb.delete(0, index);
+        }
+        assertEquals("World!", sb.toString());
+    }
+}