Resolved #53

src/main/java/strman/Strman.java

@@ -1109,6 +1109,28 @@ public abstract class Strman {
         return value.chars().mapToObj(ch -> leftPad(Integer.toString(ch, radix), "0", digits)).collect(joining());
     }
 
+
+    /**
+     * Join concatenates all the elements of the strings array into a single String. The separator string is placed between elements in the resulting string.
+     *
+     * @param strings   The input array to concatenate
+     * @param separator The separator to use
+     * @return Concatenated String
+     */
+    public static String join(final String[] strings, final String separator) {
+        if (strings == null) {
+            throw new IllegalArgumentException("Input array 'strings' can't be null");
+        }
+        if (separator == null) {
+            throw new IllegalArgumentException("separator can't be null");
+        }
+        StringJoiner joiner = new StringJoiner(separator);
+        for (String el : strings) {
+            joiner.add(el);
+        }
+        return joiner.toString();
+    }
+
     private static void validate(String value, Predicate<String> predicate, final Supplier<String> supplier) {
         if (predicate.test(value)) {
             throw new IllegalArgumentException(supplier.get());

src/test/java/strman/StrmanTest.java

@@ -411,9 +411,9 @@ public class StrmanTest {
 
     @Test
     public void inequal_shouldTestInequalityOfStrings() throws Exception {
-        assertThat(inequal("a", "b"), equalTo(true));
-        assertThat(inequal("a", "a"), equalTo(false));
-        assertThat(inequal("0", "1"), equalTo(true));
+        assertThat(unequal("a", "b"), equalTo(true));
+        assertThat(unequal("a", "a"), equalTo(false));
+        assertThat(unequal("0", "1"), equalTo(true));
     }
 
     @Test
@@ -885,4 +885,31 @@ public class StrmanTest {
                 assertThat(String.format("%s should be foo_bar", el), toSnakeCase(el), is(equalTo("foo_bar"))));
 
     }
+
+    @Test
+    public void join_shouldJoinArrayOfStringIntoASingleString() throws Exception {
+        String[] strings = {
+                "hello",
+                "world",
+                "123"
+        };
+        assertThat(join(strings, ";"), is(equalTo("hello;world;123")));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void join_shouldThrowIllegalArgumentExceptionWhenSeparatorIsNull() throws Exception {
+        String[] strings = {
+                "hello",
+                "world",
+                "123"
+        };
+
+        join(strings, null);
+    }
+
+    @Test
+    public void join_shouldReturnEmptyStringWhenInputArrayIsEmpty() throws Exception {
+        String[] emptyArray = {};
+        assertThat(join(emptyArray, ","), is(equalTo("")));
+    }
 }