diff --git a/core/src/main/java/org/jsonex/core/util/ArrayUtil.java b/core/src/main/java/org/jsonex/core/util/ArrayUtil.java
index 10d27a5..6e690c9 100644
--- a/core/src/main/java/org/jsonex/core/util/ArrayUtil.java
+++ b/core/src/main/java/org/jsonex/core/util/ArrayUtil.java
@@ -19,6 +19,10 @@ public static <T> int indexOf(@Nullable T[] array, T e) {
     return -1;
   }
 
+  public static <T> boolean contains(@Nullable T[] array, T e) {
+    return indexOf(array, e) >= 0;
+  }
+
   public static <TSrc, TDest> TDest[] map(@Nullable TSrc[] source, Function<? super TSrc, ? extends TDest> func, TDest[] dest) {
     return mapWithIndex(source, (s, idx) -> func.apply(s), dest);
   }
@@ -77,5 +81,4 @@ public static <V> int indexOf(V[] source, Predicate<? super V> pred) {
           return i;
     return -1;
   }
-
 }
diff --git a/core/src/main/java/org/jsonex/core/util/MapBuilder.java b/core/src/main/java/org/jsonex/core/util/MapBuilder.java
index bf85464..ab4d6bd 100644
--- a/core/src/main/java/org/jsonex/core/util/MapBuilder.java
+++ b/core/src/main/java/org/jsonex/core/util/MapBuilder.java
@@ -28,7 +28,11 @@ public MapBuilder() {}
   public MapBuilder(K key, V val) { put(key, val); }
   public Map<K, V> build() { return map; }
 
+  @Deprecated // Use of instead
   public static <K, V> MapBuilder<K, V> mapOf(K key, V val) {
     return new MapBuilder<>(key, val);
   }
+  public static <K, V> MapBuilder<K, V> of(K key, V val) {
+    return new MapBuilder<>(key, val);
+  }
 }
\ No newline at end of file
diff --git a/core/src/main/java/org/jsonex/core/util/TwoWayMap.java b/core/src/main/java/org/jsonex/core/util/TwoWayMap.java
new file mode 100644
index 0000000..0a68f22
--- /dev/null
+++ b/core/src/main/java/org/jsonex/core/util/TwoWayMap.java
@@ -0,0 +1,28 @@
+package org.jsonex.core.util;
+
+import lombok.Setter;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A two-way map which allow map values from key to value or reverse. This class provides default value if no match found
+ * and support chained put method.
+ */
+public class TwoWayMap<K, V> {
+  private final Map<K, V> map = new HashMap<>();
+  private final Map<V, K> reverseMap = new HashMap<>();
+  @Setter private K defaultKey;
+  @Setter private V defaultValue;
+
+  public static <K, V> TwoWayMap<K, V> of(K key, V value) { return new TwoWayMap<K, V>().put(key, value); }
+
+  public TwoWayMap<K, V> put(K key, V value) {
+    map.put(key, value);
+    reverseMap.put(value, key);
+    return this;
+  }
+
+  public V get(K key) { return key == null ? null : map.getOrDefault(key, defaultValue); }
+  public K getKey(V value) { return value == null ? null : reverseMap.getOrDefault(value, defaultKey); }
+}
\ No newline at end of file
diff --git a/core/src/test/java/org/jsonex/core/util/ArrayUtilTest.java b/core/src/test/java/org/jsonex/core/util/ArrayUtilTest.java
index d8f64e5..94af658 100644
--- a/core/src/test/java/org/jsonex/core/util/ArrayUtilTest.java
+++ b/core/src/test/java/org/jsonex/core/util/ArrayUtilTest.java
@@ -8,8 +8,7 @@
 
 import static org.jsonex.core.type.Operator.eq;
 import static org.jsonex.core.util.ListUtilTest.TestCls.F_TYPE;
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.*;
 
 public class ArrayUtilTest {
   private TestCls[] buildArray() {
@@ -43,5 +42,6 @@ private TestCls[] buildArray() {
     assertEquals(Optional.empty(), ArrayUtil.first(list, eq(F_TYPE, 3)));
     assertEquals(Optional.empty(), ArrayUtil.first(null, eq(F_TYPE, 3)));
     assertEquals(-1, ArrayUtil.indexOf(null, eq(F_TYPE, 2)));
+    assertTrue(ArrayUtil.contains(list, list[2]));
   }
 }
diff --git a/core/src/test/java/org/jsonex/core/util/TwoWayMapTest.java b/core/src/test/java/org/jsonex/core/util/TwoWayMapTest.java
new file mode 100644
index 0000000..432c970
--- /dev/null
+++ b/core/src/test/java/org/jsonex/core/util/TwoWayMapTest.java
@@ -0,0 +1,17 @@
+package org.jsonex.core.util;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+public class TwoWayMapTest {
+  @Test public void testGet() {
+    TwoWayMap map = TwoWayMap.of("a", "A").put("b", "B").setDefaultKey("+").setDefaultValue("-");
+    assertEquals("A", map.get("a"));
+    assertEquals("b", map.getKey("B"));
+    assertNull(map.getKey(null));
+    assertEquals("+", map.getKey("C"));
+    assertEquals("-", map.get("c"));
+  }
+}