Added StringUtils method to filter a string so that it becomes a vali…

…d Java identifier
rife2 · Jul 5, 2024 · 86e335e · 86e335e
1 parent d71c6f5
commit 86e335e
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diff --git a/src/main/java/rife/tools/StringUtils.java b/src/main/java/rife/tools/StringUtils.java
@@ -2481,6 +2481,46 @@ public static boolean filter(String name, Pattern[] included, Pattern[] excluded
         return accepted;
     }
 
+    /**
+     * Filters the given string by removing any characters that are not valid in a Java identifier.
+     * <p>
+     * If a valid identifier can't be generated, {@code null} will be returned.
+     *
+     * @param value the string to be filtered
+     * @return the filtered string as a valid Java identifier; or
+     * <p>{@code null} if a valid Java identifier couldn't be generated
+     * @since 1.8.0
+     */
+    public static String filterAsIdentifier(String value) {
+        if (null == value || value.isEmpty()) {
+            return null;
+        }
+
+        StringBuilder identifier = null;
+        for (int i = 0; i < value.length(); i++) {
+            var c = value.charAt(i);
+            if (identifier == null) {
+                if (!Character.isJavaIdentifierStart(c)) {
+                    identifier = new StringBuilder(value.substring(0, i));
+                }
+            }
+            else if ((identifier.isEmpty() && Character.isJavaIdentifierStart(c)) ||
+                (!identifier.isEmpty() && Character.isJavaIdentifierPart(c))) {
+                identifier.append(c);
+            }
+        }
+
+        if (identifier == null) {
+            return value;
+        }
+
+        if (identifier.isEmpty()) {
+            return null;
+        }
+
+        return identifier.toString();
+    }
+
     /**
      * Ensure that the first character of the provided string is upper case.
      *

diff --git a/src/test/java/rife/tools/TestStringUtils.java b/src/test/java/rife/tools/TestStringUtils.java
@@ -637,6 +637,35 @@ void testFilterMultipleNonMatching() {
         assertFalse(StringUtils.filter("test", new Pattern[]{Pattern.compile("x"), Pattern.compile("b")}, new Pattern[]{Pattern.compile("a"), Pattern.compile("t")}, false));
     }
 
+    @Test  void testFilterAsIdentifierWithValidString() {
+        var validIdentifier = "validIdentifier";
+        assertEquals(validIdentifier, StringUtils.filterAsIdentifier(validIdentifier));
+    }
+
+    @Test void testFilterAsIdentifierWithInvalidString() {
+        var invalidIdentifier = "1nvalidIdentifier";
+        assertEquals("nvalidIdentifier", StringUtils.filterAsIdentifier(invalidIdentifier));
+    }
+
+    @Test void testFilterAsIdentifierWithEmptyString() {
+        var emptyString = "";
+        assertNull(StringUtils.filterAsIdentifier(emptyString));
+    }
+
+    @Test void testFilterAsIdentifierWithNullValue() {
+        assertNull(StringUtils.filterAsIdentifier(null));
+    }
+
+    @Test void testFilterAsIdentifierWithInvalidCharacters() {
+        var stringWithInvalidChars = "some@string)with%invalid^chars";
+        assertEquals("somestringwithinvalidchars", StringUtils.filterAsIdentifier(stringWithInvalidChars));
+    }
+
+    @Test void testFilterAsIdentifierWithAllInvalidCharacters() {
+        var stringWithInvalidChars = "12987@)%^";
+        assertNull(StringUtils.filterAsIdentifier(stringWithInvalidChars));
+    }
+
     @Test
     void testCapitalize() {
         assertNull(StringUtils.capitalize(null));