Implemented the U.joinToString() method

Author: javadev

src/main/java/com/github/underscore/U.java

@@ -2523,6 +2523,14 @@ public static <T> String join(final Iterable<T> iterable, final String separator
         return Underscore.join(iterable, separator);
     }
 
+    public static <T> String joinToString(final Iterable<T> iterable, final String separator,
+                                  final String prefix, final String postfix,
+                                  final int limit,
+                                  final String truncated,
+                                  final Function<T, String> transform) {
+        return Underscore.joinToString(iterable, separator, prefix, postfix, limit, truncated, transform);
+    }
+
     public static String toJson(Collection collection) {
         return Json.toJson(collection);
     }

src/main/java/com/github/underscore/Underscore.java

@@ -3320,6 +3320,40 @@ public static <T> String join(final Iterable<T> iterable, final String separator
         return sb.toString();
     }
 
+    public static <T> String joinToString(final Iterable<T> iterable, final String separator,
+                                          final String prefix, final String postfix,
+                                          final int limit,
+                                          final String truncated,
+                                          final Function<T, String> transform) {
+        final StringBuilder sb = new StringBuilder();
+        int index = 0;
+        if (prefix != null) {
+            sb.append(prefix);
+        }
+        for (final T item : iterable) {
+            if (index > 0) {
+                sb.append(separator);
+            }
+            index += 1;
+            if (limit < 0 || index <= limit) {
+                sb.append(transform == null ? item.toString() : transform.apply(item));
+            } else {
+                break;
+            }
+        }
+        joinToStringPostfix(postfix, limit, truncated, index, sb);
+        return sb.toString();
+    }
+
+    private static void joinToStringPostfix(String postfix, int limit, String truncated, int index, StringBuilder sb) {
+        if (limit >= 0 && index > limit) {
+            sb.append(truncated == null ? "..." : truncated);
+        }
+        if (postfix != null) {
+            sb.append(postfix);
+        }
+    }
+
     public static <T> String join(final Iterable<T> iterable) {
         return join(iterable, " ");
     }

src/test/java/com/github/underscore/FunctionsTest.java

@@ -199,7 +199,7 @@ void defer() {
                             return null;
                         });
         assertEquals(0, counter[0].intValue(), "incr was debounced");
-        await().atLeast(60, TimeUnit.MILLISECONDS)
+        await().atLeast(90, TimeUnit.MILLISECONDS)
                 .until(
                         () -> {
                             assertEquals(1, counter[0].intValue(), "incr was debounced");

src/test/java/com/github/underscore/UnderscoreTest.java

@@ -41,6 +41,7 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Properties;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import org.junit.jupiter.api.Test;
 
@@ -117,6 +118,31 @@ void join() {
         assertEquals("--", Underscore.join(asList("", "", ""), "-"));
     }
 
+    @Test
+    void joinToString() {
+        assertEquals("[]", Underscore.joinToString(List.of(), ",", "[", "]",
+                3, "...", null));
+        assertEquals("[1,2,3]", Underscore.joinToString(List.of(1, 2, 3), ",",
+                "[", "]", -1, "...", null));
+        assertEquals("[1,2,3]", Underscore.joinToString(List.of(1, 2, 3), ",",
+                "[", "]", 3, "...", null));
+        assertEquals("[1,2,3,...]", Underscore.joinToString(List.of(1, 2, 3, 4, 5), ",",
+                "[", "]", 3, "...", null));
+        Function<Integer, String> transform = i -> "Value-" + i;
+        assertEquals("[Value-1,Value-2,Value-3]", Underscore.joinToString(List.of(1, 2, 3), ",",
+                "[", "]", -1, "...", transform));
+        assertEquals("[1,2,3]", Underscore.joinToString(List.of(1, 2, 3), ",",
+                "[", "]", -1, "...", null));
+        assertEquals("{1, 2, 3}", Underscore.joinToString(List.of(1, 2, 3), ", ",
+                "{", "}", -1, "...", null));
+        assertEquals("1, 2, ...", Underscore.joinToString(List.of(1, 2, 3, 4), ", ",
+                "", "", 2, "...", null));
+        assertEquals("1, 2, ...", Underscore.joinToString(List.of(1, 2, 3, 4), ", ",
+                null, null, 2, "...", null));
+        assertEquals("1, 2, ...", Underscore.joinToString(List.of(1, 2, 3, 4), ", ",
+                null, null, 2, null, null));
+    }
+
     /*
     _.push(['a', 'b', 'c'], 0, 2);
     // → ['a', 'b', 'c', 0, 2]

src/test/java/com/github/underscore/UtilityTest.java

@@ -478,4 +478,12 @@ void result() {
                 null,
                 Underscore.result(asList("result1", "result2"), item -> item.equals("result3")));
     }
+
+    @Test
+    void joinToString() {
+        assertEquals("[]", U.joinToString(List.of(), ",",
+                "[", "]", 3, "...", null));
+        assertEquals("[1,2,3]", U.joinToString(List.of(1, 2, 3), ",",
+                "[", "]", -1, "...", null));
+    }
 }