Add abbreviate method (#4164)

Signed-off-by: Leo Siepel <leosiepel@gmail.com>

bundles/org.openhab.core/src/main/java/org/openhab/core/util/StringUtils.java

@@ -27,6 +27,25 @@
 @NonNullByDefault
 public class StringUtils {
 
+    /**
+     * Input string is shortened to the maxwidth, the last 3 chars are replaced by ...
+     * 
+     * For example: (maxWidth 18) input="openHAB is the greatest ever", return="openHAB is the ..."
+     * 
+     * @param input input string
+     * @param maxWidth maxmimum amount of characters to return (including ...)
+     * @return Abbreviated String
+     */
+    public static @Nullable String abbreviate(final @Nullable String input, final int maxWidth) {
+        if (input != null) {
+            if (input.length() < 4 || input.length() <= maxWidth) {
+                return input;
+            }
+            return input.substring(0, maxWidth - 3) + "...";
+        }
+        return input;
+    }
+
     /**
      * If a newline char exists at the end of the line, it is removed
      *

bundles/org.openhab.core/src/test/java/org/openhab/core/util/StringUtilsTest.java

@@ -25,6 +25,17 @@
 @NonNullByDefault
 public class StringUtilsTest {
 
+    @Test
+    public void abbreviateTest() {
+        assertEquals("", StringUtils.abbreviate("", 10));
+        assertEquals(null, StringUtils.abbreviate(null, 5));
+        assertEquals("openHAB is the ...", StringUtils.abbreviate("openHAB is the greatest ever", 18));
+        assertEquals("four", StringUtils.abbreviate("four", 4));
+        assertEquals("...", StringUtils.abbreviate("four", 3));
+        assertEquals("abc", StringUtils.abbreviate("abc", 3));
+        assertEquals("abc", StringUtils.abbreviate("abc", 2));
+    }
+
     @Test
     public void chompTest() {
         assertEquals("", StringUtils.chomp(""));