Add StringUtils.removeStart(String, char).

apache · Oct 8, 2021 · e3e29d5 · e3e29d5
1 parent b153aca
commit e3e29d5
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Showing 3 changed files with 48 additions and 1 deletion.
diff --git a/src/changes/changes.xml b/src/changes/changes.xml
@@ -84,6 +84,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add SystemUtils.IS_JAVA_16.</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add ObjectUtils.identityHashCodeHex(Object).</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add ObjectUtils.hashCodeHex(Object).</action>
+    <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add StringUtils.removeStart(String, char).</action>
     <!-- UPDATE -->
     <action                   type="update" dev="ggregory" due-to="Dependabot, Gary Gregory">Bump spotbugs-maven-plugin from 4.2.0 to 4.2.3 #735.</action>
     <action                   type="update" dev="ggregory" due-to="Dependabot, XenoAmess">Bump Bump actions/cache from v2.1.4 to v2.1.6 #742, #752, #764.</action>

diff --git a/src/main/java/org/apache/commons/lang3/StringUtils.java b/src/main/java/org/apache/commons/lang3/StringUtils.java
@@ -6158,6 +6158,36 @@ public static String removePattern(final String source, final String regex) {
         return RegExUtils.removePattern(source, regex);
     }
 
+    /**
+     * Removes a char only if it is at the beginning of a source string,
+     * otherwise returns the source string.
+     *
+     * <p>A {@code null} source string will return {@code null}.
+     * An empty ("") source string will return the empty string.
+     * A {@code null} search char will return the source string.</p>
+     *
+     * <pre>
+     * StringUtils.removeStart(null, *)      = null
+     * StringUtils.removeStart("", *)        = ""
+     * StringUtils.removeStart(*, null)      = *
+     * StringUtils.removeStart("/path", '/') = "path"
+     * StringUtils.removeStart("path", '/')  = "path"
+     * StringUtils.removeStart("path", 0)    = "path"
+     * </pre>
+     *
+     * @param str  the source String to search, may be null.
+     * @param remove  the char to search for and remove.
+     * @return the substring with the char removed if found,
+     *  {@code null} if null String input.
+     * @since 3.13.0
+     */
+    public static String removeStart(final String str, final char remove) {
+        if (isEmpty(str)) {
+            return str;
+        }
+        return str.charAt(0) == remove ? str.substring(1) : str;
+    }
+
     /**
      * <p>Removes a substring only if it is at the beginning of a source string,
      * otherwise returns the source string.</p>

diff --git a/src/test/java/org/apache/commons/lang3/StringUtilsTest.java b/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
@@ -1794,7 +1794,23 @@ public void testRemovePattern_StringString() {
     }
 
     @Test
-    public void testRemoveStart() {
+    public void testRemoveStartChar() {
+        // StringUtils.removeStart("", *)        = ""
+        assertNull(StringUtils.removeStart(null, '\0'));
+        assertNull(StringUtils.removeStart(null, 'a'));
+
+        // StringUtils.removeStart(*, null)      = *
+        assertEquals(StringUtils.removeStart("", '\0'), "");
+        assertEquals(StringUtils.removeStart("", 'a'), "");
+
+        // All others:
+        assertEquals(StringUtils.removeStart("/path", '/'), "path");
+        assertEquals(StringUtils.removeStart("path", '/'), "path");
+        assertEquals(StringUtils.removeStart("path", '\0'), "path");
+    }
+
+    @Test
+    public void testRemoveStartString() {
         // StringUtils.removeStart("", *)        = ""
         assertNull(StringUtils.removeStart(null, null));
         assertNull(StringUtils.removeStart(null, ""));